Merge pull request #2206 from ehuss/bump-version

Update to 0.4.35
2025-12-28 11:24:57 -05:00 · 2023-09-29 22:43:05 +00:00 · 2023-09-29 14:33:45 -07:00 · 2023-09-29 14:33:20 -07:00 · 2023-09-22 17:26:27 +00:00 · 2023-09-19 20:44:39 +06:00
59 changed files with 2297 additions and 1050 deletions
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -3,6 +3,13 @@ on:
  release:
    types: [created]

+defaults:
+  run:
+    shell: bash
+
+permissions:
+  contents: write
+
 jobs:
  release:
    name: Deploy Release
@@ -28,17 +35,14 @@ jobs:
            os: windows-latest
    steps:
    - uses: actions/checkout@master
-    - name: Install hub
-      run: ci/install-hub.sh ${{ matrix.os }}
-      shell: bash
    - name: Install Rust
      run: ci/install-rust.sh stable ${{ matrix.target }}
-      shell: bash
-    - name: Build and deploy artifacts
+    - name: Build asset
+      run: ci/make-release-asset.sh ${{ matrix.os }} ${{ matrix.target }}
+    - name: Update release with new asset
      env:
        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      run: ci/make-release.sh ${{ matrix.os }} ${{ matrix.target }}
-      shell: bash
+      run: gh release upload $MDBOOK_TAG $MDBOOK_ASSET
  pages:
    name: GitHub Pages
    runs-on: ubuntu-latest
@@ -56,3 +60,14 @@ jobs:
        curl -LsSf https://raw.githubusercontent.com/rust-lang/simpleinfra/master/setup-deploy-keys/src/deploy.rs | rustc - -o /tmp/deploy
        cd guide/book
        /tmp/deploy
+  publish:
+    name: Publish to crates.io
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: Install Rust (rustup)
+        run: rustup update stable --no-self-update && rustup default stable
+      - name: Publish
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+        run: cargo publish --no-verify
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,10 +1,7 @@
 name: CI
 on:
-  # Only run when merging to master, or open/synchronize/reopen a PR.
-  push:
-    branches:
-      - master
  pull_request:
+  merge_group:

 jobs:
  test:
@@ -32,13 +29,13 @@ jobs:
          - build: msrv
            os: ubuntu-20.04
            # sync MSRV with docs: guide/src/guide/installation.md and Cargo.toml
-            rust: 1.60.0
+            rust: 1.66.0
    steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
    - name: Install Rust
      run: bash ci/install-rust.sh ${{ matrix.rust }}
    - name: Build and run tests
-      run: cargo test
+      run: cargo test --locked
    - name: Test no default
      run: cargo test --no-default-features

@@ -46,7 +43,24 @@ jobs:
    name: Rustfmt
    runs-on: ubuntu-latest
    steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
    - name: Install Rust
      run: rustup update stable && rustup default stable && rustup component add rustfmt
    - run: cargo fmt --check
+
+  # The success job is here to consolidate the total success/failure state of
+  # all other jobs. This job is then included in the GitHub branch protection
+  # rule which prevents merges unless all other jobs are passing. This makes
+  # it easier to manage the list of jobs via this yml file and to prevent
+  # accidentally adding new jobs without also updating the branch protections.
+  success:
+    name: Success gate
+    if: always()
+    needs:
+      - test
+      - rustfmt
+    runs-on: ubuntu-latest
+    steps:
+      - run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'
+      - name: Done
+        run: exit 0
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,133 @@
 # Changelog

+## mdBook 0.4.35
+[v0.4.34...v0.4.35](https://github.com/rust-lang/mdBook/compare/v0.4.34...v0.4.35)
+
+### Added
+- Added the `book.text-direction` setting for explicit support for right-to-left languages.
+  [#1641](https://github.com/rust-lang/mdBook/pull/1641)
+- Added `rel=prefetch` to the "next" links to potentially improve browser performance.
+  [#2168](https://github.com/rust-lang/mdBook/pull/2168)
+- Added a `.warning` CSS class which is styled for displaying warning blocks.
+  [#2187](https://github.com/rust-lang/mdBook/pull/2187)
+
+### Changed
+- Better support of the sidebar when JavaScript is disabled.
+  [#2175](https://github.com/rust-lang/mdBook/pull/2175)
+
+## mdBook 0.4.34
+[v0.4.33...v0.4.34](https://github.com/rust-lang/mdBook/compare/v0.4.33...v0.4.34)
+
+### Fixed
+- Fixed file change watcher failing on macOS with a large number of files.
+  [#2157](https://github.com/rust-lang/mdBook/pull/2157)
+
+## mdBook 0.4.33
+[v0.4.32...v0.4.33](https://github.com/rust-lang/mdBook/compare/v0.4.32...v0.4.33)
+
+### Added
+- The `color-scheme` CSS property is now set based on the light/dark theme, which applies some slight color differences in browser elements like scroll bars on some browsers.
+  [#2134](https://github.com/rust-lang/mdBook/pull/2134)
+
+### Fixed
+- Fixed watching of extra-watch-dirs when not running in the book root directory.
+  [#2146](https://github.com/rust-lang/mdBook/pull/2146)
+- Reverted the dependency update to the `toml` crate (again!). This was an unintentional breaking change in 0.4.32.
+  [#2021](https://github.com/rust-lang/mdBook/pull/2021)
+- Changed macOS change notifications to use the kqueue implementation which should fix some issues with repeated rebuilds when a file changed.
+  [#2152](https://github.com/rust-lang/mdBook/pull/2152)
+- Don't set a background color in the print page for code blocks in a header.
+  [#2150](https://github.com/rust-lang/mdBook/pull/2150)
+
+## mdBook 0.4.32
+[v0.4.31...v0.4.32](https://github.com/rust-lang/mdBook/compare/v0.4.31...v0.4.32)
+
+### Fixed
+- Fixed theme-color meta tag not syncing with the theme.
+  [#2118](https://github.com/rust-lang/mdBook/pull/2118)
+
+### Changed
+- Updated all dependencies.
+  [#2121](https://github.com/rust-lang/mdBook/pull/2121)
+  [#2122](https://github.com/rust-lang/mdBook/pull/2122)
+  [#2123](https://github.com/rust-lang/mdBook/pull/2123)
+  [#2124](https://github.com/rust-lang/mdBook/pull/2124)
+  [#2125](https://github.com/rust-lang/mdBook/pull/2125)
+  [#2126](https://github.com/rust-lang/mdBook/pull/2126)
+
+## mdBook 0.4.31
+[v0.4.30...v0.4.31](https://github.com/rust-lang/mdBook/compare/v0.4.30...v0.4.31)
+
+### Fixed
+- Fixed menu border render flash during page navigation.
+  [#2101](https://github.com/rust-lang/mdBook/pull/2101)
+- Fixed flicker setting sidebar scroll position.
+  [#2104](https://github.com/rust-lang/mdBook/pull/2104)
+- Fixed compile error with proc-macro2 on latest Rust nightly.
+  [#2109](https://github.com/rust-lang/mdBook/pull/2109)
+
+## mdBook 0.4.30
+[v0.4.29...v0.4.30](https://github.com/rust-lang/mdBook/compare/v0.4.29...v0.4.30)
+
+### Added
+- Added support for heading attributes.
+  Attributes are specified in curly braces just after the heading text.
+  An HTML ID can be specified with `#` and classes with `.`.
+  For example: `## My heading {#custom-id .class1 .class2}`
+  [#2013](https://github.com/rust-lang/mdBook/pull/2013)
+- Added support for hidden code lines for languages other than Rust.
+  The `output.html.code.hidelines` table allows you to define the prefix character that will be used to hide code lines based on the language.
+  [#2093](https://github.com/rust-lang/mdBook/pull/2093)
+
+### Fixed
+- Fixed a few minor markdown rendering issues.
+  [#2092](https://github.com/rust-lang/mdBook/pull/2092)
+
+## mdBook 0.4.29
+[v0.4.28...v0.4.29](https://github.com/rust-lang/mdBook/compare/v0.4.28...v0.4.29)
+
+### Changed
+- Built-in fonts are no longer copied when `fonts/fonts.css` is overridden in the theme directory.
+  Additionally, the warning about `copy-fonts` has been removed if `fonts/fonts.css` is specified.
+  [#2080](https://github.com/rust-lang/mdBook/pull/2080)
+- `mdbook init --force` now skips all interactive prompts as intended.
+  [#2057](https://github.com/rust-lang/mdBook/pull/2057)
+- Updated dependencies
+  [#2063](https://github.com/rust-lang/mdBook/pull/2063)
+  [#2086](https://github.com/rust-lang/mdBook/pull/2086)
+  [#2082](https://github.com/rust-lang/mdBook/pull/2082)
+  [#2084](https://github.com/rust-lang/mdBook/pull/2084)
+  [#2085](https://github.com/rust-lang/mdBook/pull/2085)
+
+### Fixed
+- Switched from the `gitignore` library to `ignore`. This should bring some improvements with gitignore handling.
+  [#2076](https://github.com/rust-lang/mdBook/pull/2076)
+
+## mdBook 0.4.28
+[v0.4.27...v0.4.28](https://github.com/rust-lang/mdBook/compare/v0.4.27...v0.4.28)
+
+### Changed
+- The sidebar is now shown on wide screens when localstorage is disabled.
+  [#2017](https://github.com/rust-lang/mdBook/pull/2017)
+- Preprocessors are now run with `mdbook test`.
+  [#1986](https://github.com/rust-lang/mdBook/pull/1986)
+
+### Fixed
+- Fixed regression in 0.4.26 that prevented the title bar from scrolling properly on smaller screens.
+  [#2039](https://github.com/rust-lang/mdBook/pull/2039)
+
+## mdBook 0.4.27
+[v0.4.26...v0.4.27](https://github.com/rust-lang/mdBook/compare/v0.4.26...v0.4.27)
+
+### Changed
+- Reverted the dependency update to the `toml` crate. This was an unintentional breaking change in 0.4.26.
+  [#2021](https://github.com/rust-lang/mdBook/pull/2021)
+
 ## mdBook 0.4.26
 [v0.4.25...v0.4.26](https://github.com/rust-lang/mdBook/compare/v0.4.25...v0.4.26)

+**The 0.4.26 release has been yanked due to an unintentional breaking change.**
+
 ### Changed
 - Removed custom scrollbars for webkit browsers
  [#1961](https://github.com/rust-lang/mdBook/pull/1961)
@@ -154,7 +279,7 @@
  [#1771](https://github.com/rust-lang/mdBook/pull/1771)
 - The 404 not-found page now includes the books title in the HTML title tag.
  [#1693](https://github.com/rust-lang/mdBook/pull/1693)
- Migrated to clap 3.0 which which handles CLI option parsing.
+- Migrated to clap 3.0 which handles CLI option parsing.
  [#1731](https://github.com/rust-lang/mdBook/pull/1731)

 ### Fixed
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -153,3 +153,23 @@ The following are instructions for updating [highlight.js](https://highlightjs.o
 1. Copy `build/highlight.min.js` to mdbook's directory [`highlight.js`](https://github.com/rust-lang/mdBook/blob/master/src/theme/highlight.js).
 1. Be sure to check the highlight.js [CHANGES](https://github.com/highlightjs/highlight.js/blob/main/CHANGES.md) for any breaking changes. Breaking changes that would affect users will need to wait until the next major release.
 1. Build mdbook with the new file and build some books with the new version and compare the output with a variety of languages to see if anything changes. The [test_book](https://github.com/rust-lang/mdBook/tree/master/test_book) contains a chapter with many languages to examine.
+
+## Publishing new releases
+
+Instructions for mdBook maintainers to publish a new release:
+
+1. Create a PR to update the version and update the CHANGELOG:
+    1. Update the version in `Cargo.toml`
+    2. Run `cargo test` to verify that everything is passing, and to update `Cargo.lock`.
+    3. Double-check for any SemVer breaking changes.
+       Try [`cargo-semver-checks`](https://crates.io/crates/cargo-semver-checks), though beware that the current version of mdBook isn't properly adhering to SemVer due to the lack of `#[non_exhaustive]` and other issues. See https://github.com/rust-lang/mdBook/issues/1835.
+    4. Update `CHANGELOG.md` with any changes that users may be interested in.
+    5. Update `continuous-integration.md` to update the version number for the installation instructions.
+    6. Commit the changes, and open a PR.
+2. After the PR has been merged, create a release in GitHub. This can either be done in the GitHub web UI, or on the command-line:
+   ```bash
+   MDBOOK_VERS="`cargo read-manifest | jq -r .version`" ; \
+    gh release create -R rust-lang/mdbook v$MDBOOK_VERS \
+        --title v$MDBOOK_VERS \
+        --notes "See https://github.com/rust-lang/mdBook/blob/master/CHANGELOG.md#mdbook-${MDBOOK_VERS//.} for a complete list of changes."
+   ```
--- a/Cargo.lock
+++ b/Cargo.lock
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mdbook"
-version = "0.4.26"
+version = "0.4.35"
 authors = [
    "Mathieu David <mathieudavid@mathieudavid.org>",
    "Michael-F-Bryan <michaelfbryan@gmail.com>",
@@ -14,55 +14,55 @@ license = "MPL-2.0"
 readme = "README.md"
 repository = "https://github.com/rust-lang/mdBook"
 description = "Creates a book from markdown files"
-rust-version = "1.60"
+rust-version = "1.66"

 [dependencies]
-anyhow = "1.0.28"
-chrono = { version = "0.4", default-features = false, features = ["clock"] }
-clap = { version = "4.0.29", features = ["cargo", "wrap_help"] }
-clap_complete = "4.0.6"
-once_cell = "1"
+anyhow = "1.0.71"
+chrono = { version = "0.4.24", default-features = false, features = ["clock"] }
+clap = { version = "4.3.12", features = ["cargo", "wrap_help"] }
+clap_complete = "4.3.2"
+once_cell = "1.17.1"
 env_logger = "0.10.0"
-handlebars = "4.0"
-log = "0.4"
-memchr = "2.0"
-opener = "0.5"
-pulldown-cmark = { version = "0.9.1", default-features = false }
-regex = "1.5.5"
-serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
-shlex = "1"
-tempfile = "3.0"
-toml = "0.7.2"
+handlebars = "4.3.7"
+log = "0.4.17"
+memchr = "2.5.0"
+opener = "0.6.1"
+pulldown-cmark = { version = "0.9.3", default-features = false }
+regex = "1.8.1"
+serde = { version = "1.0.163", features = ["derive"] }
+serde_json = "1.0.96"
+shlex = "1.1.0"
+tempfile = "3.4.0"
+toml = "0.5.11" # Do not update, see https://github.com/rust-lang/mdBook/issues/2037
 topological-sort = "0.2.2"

 # Watch feature
-notify = { version = "5.0.0", optional = true }
-notify-debouncer-mini = { version = "0.2.1", optional = true }
-gitignore = { version = "1.0", optional = true }
+notify = { version = "6.0.1", optional = true }
+notify-debouncer-mini = { version = "0.3.0", optional = true }
+ignore = { version = "0.4.20", optional = true }

 # Serve feature
-futures-util = { version = "0.3.4", optional = true }
-tokio = { version = "1", features = ["macros", "rt-multi-thread"], optional = true }
-warp = { version = "0.3.2", default-features = false, features = ["websocket"], optional = true }
+futures-util = { version = "0.3.28", optional = true }
+tokio = { version = "1.28.1", features = ["macros", "rt-multi-thread"], optional = true }
+warp = { version = "0.3.5", default-features = false, features = ["websocket"], optional = true }

 # Search feature
-elasticlunr-rs = { version = "3.0.0", optional = true }
-ammonia = { version = "3", optional = true }
+elasticlunr-rs = { version = "3.0.2", optional = true }
+ammonia = { version = "3.3.0", optional = true }

 [dev-dependencies]
-assert_cmd = "2.0.7"
-predicates = "2"
+assert_cmd = "2.0.11"
+predicates = "3.0.3"
 select = "0.6.0"
-semver = "1.0"
-pretty_assertions = "1.2.1"
-walkdir = "2.0"
+semver = "1.0.17"
+pretty_assertions = "1.3.0"
+walkdir = "2.3.3"

 [features]
 default = ["watch", "serve", "search"]
-watch = ["notify", "notify-debouncer-mini", "gitignore"]
-serve = ["futures-util", "tokio", "warp"]
-search = ["elasticlunr-rs", "ammonia"]
+watch = ["dep:notify", "dep:notify-debouncer-mini", "dep:ignore"]
+serve = ["dep:futures-util", "dep:tokio", "dep:warp"]
+search = ["dep:elasticlunr-rs", "dep:ammonia"]

 [[bin]]
 doc = false
--- a/ci/install-hub.sh
+++ b/ci/install-hub.sh
@@ -1,24 +0,0 @@
-#!/usr/bin/env bash
-# Installs the `hub` executable into hub/bin
-set -ex
-case $1 in
-  ubuntu*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-linux-amd64-2.12.8.tgz -o hub.tgz
-    mkdir hub
-    tar -xzvf hub.tgz --strip=1 -C hub
-    ;;
-  macos*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-darwin-amd64-2.12.8.tgz -o hub.tgz
-    mkdir hub
-    tar -xzvf hub.tgz --strip=1 -C hub
-    ;;
-  windows*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-windows-amd64-2.12.8.zip -o hub.zip
-    7z x hub.zip -ohub
-    ;;
-  *)
-    echo "OS should be first parameter, was: $1"
-    ;;
-esac
-
-echo "$PWD/hub/bin" >> $GITHUB_PATH
--- a/ci/make-release-asset.sh
+++ b/ci/make-release-asset.sh
@@ -17,7 +17,7 @@ then
  export "CARGO_TARGET_$(echo $target | tr a-z- A-Z_)_LINKER"=rust-lld
 fi
 export CARGO_PROFILE_RELEASE_LTO=true
-cargo build --bin mdbook --release --target $target
+cargo build --locked --bin mdbook --release --target $target
 cd target/$target/release
 case $1 in
  ubuntu*)
@@ -44,9 +44,10 @@ case $1 in
 esac
 cd ../..

-if [[ -z "$GITHUB_TOKEN" ]]
+if [[ -z "$GITHUB_ENV" ]]
 then
-  echo "$GITHUB_TOKEN not set, skipping deploy."
+  echo "GITHUB_ENV not set, run: gh release upload $TAG target/$asset"
 else
-  hub release edit -m "" --attach $asset $TAG
+  echo "MDBOOK_TAG=$TAG" >> $GITHUB_ENV
+  echo "MDBOOK_ASSET=target/$asset" >> $GITHUB_ENV
 fi
--- a/guide/book.toml
+++ b/guide/book.toml
@@ -17,6 +17,9 @@ edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path
 editable = true
 line-numbers = true

+[output.html.code.hidelines]
+python = "~"
+
 [output.html.search]
 limit-results = 20
 use-boolean-and = true
--- a/guide/src/cli/completions.md
+++ b/guide/src/cli/completions.md
@@ -6,7 +6,11 @@ This means when you type `mdbook` in your shell, you can then press your shell's
 The completions first need to be installed for your shell:

 ```bash
+# bash
 mdbook completions bash > ~/.local/share/bash-completion/completions/mdbook
+# oh-my-zsh
+mdbook completions zsh > ~/.oh-my-zsh/completions/_mdbook
+autoload -U compinit && compinit
 ```

 The command prints a completion script for the given shell.
--- a/guide/src/cli/init.md
+++ b/guide/src/cli/init.md
@@ -67,4 +67,16 @@ mdbook init --title="my amazing book"
 Create a `.gitignore` file configured to ignore the `book` directory created when [building] a book. 
 If not supplied, an interactive prompt will ask whether it should be created.

+```bash
+mdbook init --ignore=none
+```
+
+```bash
+mdbook init --ignore=git
+```
+
 [building]: build.md
+
+#### --force
+
+Skip the prompts to create a `.gitignore` and for the title for the book.
--- a/guide/src/cli/test.md
+++ b/guide/src/cli/test.md
@@ -6,8 +6,7 @@ of code examples that could get outdated. Therefore it is very important for
 them to be able to automatically test these code examples.

 mdBook supports a `test` command that will run all available tests in a book. At
-the moment, only rustdoc tests are supported, but this may be expanded upon in
-the future.
+the moment, only Rust tests are supported.

 #### Disable tests on a code block

@@ -65,4 +64,4 @@ not specified it will default to the value of the `build.build-dir` key in
 #### --chapter

 The `--chapter` (`-c`) option allows you to test a specific chapter of the
-book using the chapter name or the relative path to the chapter.
+book using the chapter name or the relative path to the chapter.
--- a/guide/src/continuous-integration.md
+++ b/guide/src/continuous-integration.md
@@ -21,7 +21,7 @@ A simple approach would be to use the popular `curl` CLI tool to download the ex

 ```sh
 mkdir bin
-curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.26/mdbook-v0.4.26-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
+curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.35/mdbook-v0.4.35-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
 bin/mdbook build
 ```

@@ -83,7 +83,7 @@ Or if you have your own style checks, spell checker, or any other tests it might
 ## Deploying

 You may want to automatically deploy your book.
-Some may want to do this with every time a change is pushed, and others may want to only deploy when a specific release is tagged.
+Some may want to do this every time a change is pushed, and others may want to only deploy when a specific release is tagged.

 You'll also need to understand the specifics on how to push a change to your web service.
 For example, [GitHub Pages] just requires committing the output onto a specific git branch.
--- a/guide/src/format/configuration/general.md
+++ b/guide/src/format/configuration/general.md
@@ -46,6 +46,9 @@ This is general information about your book.
  `src` directly under the root folder. But this is configurable with the `src`
  key in the configuration file.
 - **language:** The main language of the book, which is used as a language attribute `<html lang="en">` for example.
+  This is also used to derive the direction of text (RTL, LTR) within the book.
+- **text-direction**: The direction of text in the book: Left-to-right (LTR) or Right-to-left (RTL). Possible values: `ltr`, `rtl`.
+  When not specified, the text direction is derived from the book's `language` attribute.

 **book.toml**
 ```toml
@@ -55,6 +58,7 @@ authors = ["John Doe", "Jane Doe"]
 description = "The example book covers examples."
 src = "my-src"  # the source files will be found in `root/my-src` instead of `root/src`
 language = "en"
+text-direction = "ltr"
 ```

 ### Rust options
@@ -97,7 +101,7 @@ extra-watch-dirs = []             # directories to watch for triggering builds
  will be created when the book is built (i.e. `create-missing = true`). If this
  is `false` then the build process will instead exit with an error if any files
  do not exist.
- **use-default-preprocessors:** Disable the default preprocessors of (`links` &
+- **use-default-preprocessors:** Disable the default preprocessors (of `links` &
  `index`) by setting this option to `false`.

  If you have the same, and/or other preprocessors declared via their table
@@ -111,4 +115,4 @@ extra-watch-dirs = []             # directories to watch for triggering builds
    `use-default-preprocessors` that `links` it will run.
 - **extra-watch-dirs**: A list of paths to directories that will be watched in
  the `watch` and `serve` commands. Changes to files under these directories will
-  trigger rebuilds. Useful if your book depends on files outside its `src` directory.
+  trigger rebuilds. Useful if your book depends on files outside its `src` directory.
--- a/guide/src/format/configuration/preprocessors.md
+++ b/guide/src/format/configuration/preprocessors.md
@@ -35,7 +35,7 @@ For example, if you have a preprocessor called `mdbook-example`, then you can in
 With this table, mdBook will execute the `mdbook-example` preprocessor.

 This table can include additional key-value pairs that are specific to the preprocessor.
-For example, if our example prepocessor needed some extra configuration options:
+For example, if our example preprocessor needed some extra configuration options:

 ```toml
 [preprocessor.example]
--- a/guide/src/format/configuration/renderers.md
+++ b/guide/src/format/configuration/renderers.md
@@ -150,9 +150,9 @@ The following configuration options are available:
 - **edit-url-template:** Edit url template, when provided shows a
  "Suggest an edit" button (which looks like <i class="fa fa-edit"></i>) for directly jumping to editing the currently
  viewed page. For e.g. GitHub projects set this to
-  `https://github.com/<owner>/<repo>/edit/master/{path}` or for
+  `https://github.com/<owner>/<repo>/edit/<branch>/{path}` or for
  Bitbucket projects set it to
-  `https://bitbucket.org/<owner>/<repo>/src/master/{path}?mode=edit`
+  `https://bitbucket.org/<owner>/<repo>/src/<branch>/{path}?mode=edit`
  where {path} will be replaced with the full path of the file in the
  repository.
 - **input-404:** The name of the markdown file used for missing files.
@@ -182,7 +182,7 @@ page-break = true # insert page-break after each chapter

 - **enable:** Enable print support. When `false`, all print support will not be
  rendered. Defaults to `true`.
- **page-break** Insert page breaks between chapters. Defaults to `true`.
+- **page-break:** Insert page breaks between chapters. Defaults to `true`.

 ### `[output.html.fold]`

@@ -218,11 +218,25 @@ runnable = true          # displays a run button for rust code
 - **copyable:** Display the copy button on code snippets. Defaults to `true`.
 - **copy-js:** Copy JavaScript files for the editor to the output directory.
  Defaults to `true`.
- **line-numbers** Display line numbers on editable sections of code. Requires both `editable` and `copy-js` to be `true`. Defaults to `false`.
- **runnable** Displays a run button for rust code snippets. Changing this to `false` will disable the run in playground feature globally. Defaults to `true`.
+- **line-numbers:** Display line numbers on editable sections of code. Requires both `editable` and `copy-js` to be `true`. Defaults to `false`.
+- **runnable:** Displays a run button for rust code snippets. Changing this to `false` will disable the run in playground feature globally. Defaults to `true`.

 [Ace]: https://ace.c9.io/

+### `[output.html.code]`
+
+The `[output.html.code]` table provides options for controlling code blocks.
+
+```toml
+[output.html.code]
+# A prefix string per language (one or more chars).
+# Any line starting with whitespace+prefix is hidden.
+hidelines = { python = "~" }
+```
+
+- **hidelines:** A table that defines how [hidden code lines](../mdbook.md#hiding-code-lines) work for each language.
+  The key is the language and the value is a string that will cause code lines starting with that prefix to be hidden.
+
 ### `[output.html.search]`

 The `[output.html.search]` table provides options for controlling the built-in text [search].
--- a/guide/src/format/markdown.md
+++ b/guide/src/format/markdown.md
@@ -73,14 +73,14 @@ Linking to a URL or local file is easy:
 ```markdown
 Use [mdBook](https://github.com/rust-lang/mdBook). 

-Read about [mdBook](mdBook.md).
+Read about [mdBook](mdbook.md).

 A bare url: <https://www.rust-lang.org>.
 ```

 Use [mdBook](https://github.com/rust-lang/mdBook). 

-Read about [mdBook](mdBook.md).
+Read about [mdBook](mdbook.md).

 A bare url: <https://www.rust-lang.org>.

@@ -124,7 +124,7 @@ mdBook has several extensions beyond the standard CommonMark specification.
 ### Strikethrough

 Text may be rendered with a horizontal line through the center by wrapping the
-text with two tilde characters on each side:
+text with one or two tilde characters on each side:

 ```text
 An example of ~~strikethrough text~~.
@@ -220,3 +220,16 @@ To enable it, see the [`output.html.curly-quotes`] config option.
 [tables]: https://github.github.com/gfm/#tables-extension-
 [task list extension]: https://github.github.com/gfm/#task-list-items-extension-
 [`output.html.curly-quotes`]: configuration/renderers.md#html-renderer-options
+
+### Heading attributes
+
+Headings can have a custom HTML ID and classes. This lets you maintain the same ID even if you change the heading's text, it also lets you add multiple classes in the heading.
+
+Example:
+```md
+# Example heading { #first .class1 .class2 }
+```
+
+This makes the level 1 heading with the content `Example heading`, ID `first`, and classes `class1` and `class2`. Note that the attributes should be space-separated.
+
+More information can be found in the [heading attrs spec page](https://github.com/raphlinus/pulldown-cmark/blob/master/specs/heading_attrs.txt).
--- a/guide/src/format/mdbook.md
+++ b/guide/src/format/mdbook.md
@@ -2,11 +2,11 @@

 ## Hiding code lines

-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#` [like you would with Rustdoc][rustdoc-hide].
-This currently only works with Rust language code blocks.
+There is a feature in mdBook that lets you hide code lines by prepending them with a specific prefix.

-[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
+For the Rust language, you can use the `#` character as a prefix which will hide lines [like you would with Rustdoc][rustdoc-hide].
+
+[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/write-documentation/documentation-tests.html#hiding-portions-of-the-example

 ```bash
 # fn main() {
@@ -28,7 +28,47 @@ Will render as
 # }
 ```

-The code block has an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
+When you tap or hover the mouse over the code block, there will be an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
+
+By default, this only works for code examples that are annotated with `rust`.
+However, you can define custom prefixes for other languages by adding a new line-hiding prefix in your `book.toml` with the language name and prefix character(s):
+
+```toml
+[output.html.code.hidelines]
+python = "~"
+```
+
+The prefix will hide any lines that begin with the given prefix. With the python prefix shown above, this:
+
+```bash
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+will render as
+
+```python
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+This behavior can be overridden locally with a different prefix. This has the same effect as above:
+
+~~~markdown
+```python,hidelines=!!!
+!!!hidden()
+nothidden():
+!!!    hidden()
+    !!!hidden()
+    nothidden()
+```
+~~~

 ## Rust Playground

@@ -274,3 +314,51 @@ contents (sidebar) by including a `\{{#title ...}}` near the top of the page.
 ```hbs
 \{{#title My Title}}
 ```
+
+## HTML classes provided by mdBook
+
+<img class="right" src="images/rust-logo-blk.svg" alt="The Rust logo">
+
+### `class="left"` and `"right"`
+
+These classes are provided by default, for inline HTML to float images.
+
+```html
+<img class="right" src="images/rust-logo-blk.svg" alt="The Rust logo">
+```
+
+### `class="hidden"`
+
+HTML tags with class `hidden` will not be shown.
+
+```html
+<div class="hidden">This will not be seen.</div>
+```
+
+<div class="hidden">This will not be seen.</div>
+
+### `class="warning"`
+
+To make a warning or similar note stand out, wrap it in a warning div.
+
+```html
+<div class="warning">
+
+This is a bad thing that you should pay attention to.
+
+Warning blocks should be used sparingly in documentation, to avoid "warning
+fatique," where people are trained to ignore them because they usually don't
+matter for what they're doing.
+
+</div>
+```
+
+<div class="warning">
+
+This is a bad thing that you should pay attention to.
+
+Warning blocks should be used sparingly in documentation, to avoid "warning
+fatique," where people are trained to ignore them because they usually don't
+matter for what they're doing.
+
+</div>
--- a/guide/src/format/theme/README.md
+++ b/guide/src/format/theme/README.md
@@ -1,6 +1,6 @@
 # Theme

-The default renderer uses a [handlebars](http://handlebarsjs.com/) template to
+The default renderer uses a [handlebars](https://handlebarsjs.com) template to
 render your markdown files and comes with a default theme included in the mdBook
 binary.

--- a/guide/src/format/theme/syntax-highlighting.md
+++ b/guide/src/format/theme/syntax-highlighting.md
@@ -77,38 +77,6 @@ the `theme` folder of your book.

 Now your theme will be used instead of the default theme.

-## Hiding code lines
-
-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#`.
-
-
-```bash
-# fn main() {
-    let x = 5;
-    let y = 6;
-
-    println!("{}", x + y);
-# }
-```
-
-Will render as
-
-```rust
-# fn main() {
-    let x = 5;
-    let y = 7;
-
-    println!("{}", x + y);
-# }
-```
-
-**At the moment, this only works for code examples that are annotated with
-`rust`. Because it would collide with semantics of some programming languages.
-In the future, we want to make this configurable through the `book.toml` so that
-everyone can benefit from it.**
-
-
 ## Improve default theme

 If you think the default theme doesn't look quite right for a specific language,
--- a/guide/src/guide/installation.md
+++ b/guide/src/guide/installation.md
@@ -20,7 +20,7 @@ To make it easier to run, put the path to the binary into your `PATH`.

 To build the `mdbook` executable from source, you will first need to install Rust and Cargo.
 Follow the instructions on the [Rust installation page].
-mdBook currently requires at least Rust version 1.60.
+mdBook currently requires at least Rust version 1.66.

 Once you have installed Rust, the following command can be used to build and install mdBook:

--- a/src/book/book.rs
+++ b/src/book/book.rs
@@ -39,9 +39,7 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
        .chain(summary.suffix_chapters.iter())
        .collect();

-    while !items.is_empty() {
-        let next = items.pop().expect("already checked");
-
+    while let Some(next) = items.pop() {
        if let SummaryItem::Link(ref link) = *next {
            if let Some(ref location) = link.location {
                let filename = src_dir.join(location);
@@ -277,7 +275,7 @@ fn load_chapter<P: AsRef<Path>>(
        }

        let stripped = location
-            .strip_prefix(&src_dir)
+            .strip_prefix(src_dir)
            .expect("Chapters are always inside a book");

        Chapter::new(&link.name, content, stripped, parent_names.clone())
@@ -317,7 +315,7 @@ impl<'a> Iterator for BookItems<'a> {
    fn next(&mut self) -> Option<Self::Item> {
        let item = self.items.pop_front();

-        if let Some(&BookItem::Chapter(ref ch)) = item {
+        if let Some(BookItem::Chapter(ch)) = item {
            // if we wanted a breadth-first iterator we'd `extend()` here
            for sub_item in ch.sub_items.iter().rev() {
                self.items.push_front(sub_item);
--- a/src/book/init.rs
+++ b/src/book/init.rs
@@ -99,9 +99,7 @@ impl BookBuilder {
    fn write_book_toml(&self) -> Result<()> {
        debug!("Writing book.toml");
        let book_toml = self.root.join("book.toml");
-        let cfg = toml::to_string(&self.config)
-            .with_context(|| "Unable to serialize the config")?
-            .into_bytes();
+        let cfg = toml::to_vec(&self.config).with_context(|| "Unable to serialize the config")?;

        File::create(book_toml)
            .with_context(|| "Couldn't create book.toml")?
@@ -200,8 +198,7 @@ impl BookBuilder {
            writeln!(f, "- [Chapter 1](./chapter_1.md)")?;

            let chapter_1 = src_dir.join("chapter_1.md");
-            let mut f =
-                File::create(&chapter_1).with_context(|| "Unable to create chapter_1.md")?;
+            let mut f = File::create(chapter_1).with_context(|| "Unable to create chapter_1.md")?;
            writeln!(f, "# Chapter 1")?;
        } else {
            trace!("Existing summary found, no need to create stub files.");
@@ -214,10 +211,10 @@ impl BookBuilder {
        fs::create_dir_all(&self.root)?;

        let src = self.root.join(&self.config.book.src);
-        fs::create_dir_all(&src)?;
+        fs::create_dir_all(src)?;

        let build = self.root.join(&self.config.build.build_dir);
-        fs::create_dir_all(&build)?;
+        fs::create_dir_all(build)?;

        Ok(())
    }
--- a/src/book/mod.rs
+++ b/src/book/mod.rs
@@ -99,7 +99,7 @@ impl MDBook {
        let root = book_root.into();

        let src_dir = root.join(&config.book.src);
-        let book = book::load_book(&src_dir, &config.build)?;
+        let book = book::load_book(src_dir, &config.build)?;

        let renderers = determine_renderers(&config);
        let preprocessors = determine_preprocessors(&config)?;
@@ -122,7 +122,7 @@ impl MDBook {
        let root = book_root.into();

        let src_dir = root.join(&config.book.src);
-        let book = book::load_book_from_disk(&summary, &src_dir)?;
+        let book = book::load_book_from_disk(&summary, src_dir)?;

        let renderers = determine_renderers(&config);
        let preprocessors = determine_preprocessors(&config)?;
@@ -196,21 +196,26 @@ impl MDBook {
        Ok(())
    }

-    /// Run the entire build process for a particular [`Renderer`].
-    pub fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
-        let mut preprocessed_book = self.book.clone();
+    /// Run preprocessors and return the final book.
+    pub fn preprocess_book(&self, renderer: &dyn Renderer) -> Result<(Book, PreprocessorContext)> {
        let preprocess_ctx = PreprocessorContext::new(
            self.root.clone(),
            self.config.clone(),
            renderer.name().to_string(),
        );
-
+        let mut preprocessed_book = self.book.clone();
        for preprocessor in &self.preprocessors {
            if preprocessor_should_run(&**preprocessor, renderer, &self.config) {
                debug!("Running the {} preprocessor.", preprocessor.name());
                preprocessed_book = preprocessor.run(&preprocess_ctx, preprocessed_book)?;
            }
        }
+        Ok((preprocessed_book, preprocess_ctx))
+    }
+
+    /// Run the entire build process for a particular [`Renderer`].
+    pub fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
+        let (preprocessed_book, preprocess_ctx) = self.preprocess_book(renderer)?;

        let name = renderer.name();
        let build_dir = self.build_dir_for(name);
@@ -264,13 +269,25 @@ impl MDBook {

        let mut chapter_found = false;

-        // FIXME: Is "test" the proper renderer name to use here?
-        let preprocess_context =
-            PreprocessorContext::new(self.root.clone(), self.config.clone(), "test".to_string());
+        struct TestRenderer;
+        impl Renderer for TestRenderer {
+            // FIXME: Is "test" the proper renderer name to use here?
+            fn name(&self) -> &str {
+                "test"
+            }

-        let book = LinkPreprocessor::new().run(&preprocess_context, self.book.clone())?;
-        // Index Preprocessor is disabled so that chapter paths continue to point to the
-        // actual markdown files.
+            fn render(&self, _: &RenderContext) -> Result<()> {
+                Ok(())
+            }
+        }
+
+        // Index Preprocessor is disabled so that chapter paths
+        // continue to point to the actual markdown files.
+        self.preprocessors = determine_preprocessors(&self.config)?
+            .into_iter()
+            .filter(|pre| pre.name() != IndexPreprocessor::NAME)
+            .collect();
+        let (book, _) = self.preprocess_book(&TestRenderer)?;

        let mut failed = false;
        for item in book.iter() {
@@ -292,7 +309,7 @@ impl MDBook {
                info!("Testing chapter '{}': {:?}", ch.name, chapter_path);

                // write preprocessed file to tempdir
-                let path = temp_dir.path().join(&chapter_path);
+                let path = temp_dir.path().join(chapter_path);
                let mut tmpf = utils::fs::create_file(&path)?;
                tmpf.write_all(ch.content.as_bytes())?;

@@ -302,13 +319,13 @@ impl MDBook {
                if let Some(edition) = self.config.rust.edition {
                    match edition {
                        RustEdition::E2015 => {
-                            cmd.args(&["--edition", "2015"]);
+                            cmd.args(["--edition", "2015"]);
                        }
                        RustEdition::E2018 => {
-                            cmd.args(&["--edition", "2018"]);
+                            cmd.args(["--edition", "2018"]);
                        }
                        RustEdition::E2021 => {
-                            cmd.args(&["--edition", "2021"]);
+                            cmd.args(["--edition", "2021"]);
                        }
                    }
                }
--- a/src/cmd/build.rs
+++ b/src/cmd/build.rs
@@ -16,7 +16,7 @@ pub fn make_subcommand() -> Command {
 // Build command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
    let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;

    if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
        book.config.build.build_dir = dest_dir.into();
--- a/src/cmd/clean.rs
+++ b/src/cmd/clean.rs
@@ -16,7 +16,7 @@ pub fn make_subcommand() -> Command {
 // Clean command implementation
 pub fn execute(args: &ArgMatches) -> mdbook::errors::Result<()> {
    let book_dir = get_book_dir(args);
-    let book = MDBook::load(&book_dir)?;
+    let book = MDBook::load(book_dir)?;

    let dir_to_remove = match args.get_one::<PathBuf>("dest-dir") {
        Some(dest_dir) => dest_dir.into(),
--- a/src/cmd/init.rs
+++ b/src/cmd/init.rs
@@ -56,7 +56,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
            "git" => builder.create_gitignore(true),
            _ => builder.create_gitignore(false),
        };
-    } else {
+    } else if !args.get_flag("force") {
        println!("\nDo you want a .gitignore to be created? (y/n)");
        if confirm() {
            builder.create_gitignore(true);
@@ -65,6 +65,8 @@ pub fn execute(args: &ArgMatches) -> Result<()> {

    config.book.title = if args.contains_id("title") {
        args.get_one::<String>("title").map(String::from)
+    } else if args.get_flag("force") {
+        None
    } else {
        request_book_title()
    };
@@ -84,7 +86,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
 /// Obtains author name from git config file by running the `git config` command.
 fn get_author_name() -> Option<String> {
    let output = Command::new("git")
-        .args(&["config", "--get", "user.name"])
+        .args(["config", "--get", "user.name"])
        .output()
        .ok()?;

@@ -114,5 +116,5 @@ fn confirm() -> bool {
    io::stdout().flush().unwrap();
    let mut s = String::new();
    io::stdin().read_line(&mut s).ok();
-    matches!(&*s.trim(), "Y" | "y" | "yes" | "Yes")
+    matches!(s.trim(), "Y" | "y" | "yes" | "Yes")
 }
--- a/src/cmd/serve.rs
+++ b/src/cmd/serve.rs
@@ -48,7 +48,7 @@ pub fn make_subcommand() -> Command {
 // Serve command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
    let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;

    let port = args.get_one::<String>("port").unwrap();
    let hostname = args.get_one::<String>("hostname").unwrap();
@@ -102,7 +102,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
        info!("Building book...");

        // FIXME: This area is really ugly because we need to re-set livereload :(
-        let result = MDBook::load(&book_dir).and_then(|mut b| {
+        let result = MDBook::load(book_dir).and_then(|mut b| {
            update_config(&mut b);
            b.build()
        });
--- a/src/cmd/test.rs
+++ b/src/cmd/test.rs
@@ -44,7 +44,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
    let chapter: Option<&str> = args.get_one::<String>("chapter").map(|s| s.as_str());

    let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;

    if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
        book.config.build.build_dir = dest_dir.to_path_buf();
--- a/src/cmd/watch.rs
+++ b/src/cmd/watch.rs
@@ -1,5 +1,6 @@
 use super::command_prelude::*;
 use crate::{get_book_dir, open};
+use ignore::gitignore::Gitignore;
 use mdbook::errors::Result;
 use mdbook::utils;
 use mdbook::MDBook;
@@ -20,7 +21,7 @@ pub fn make_subcommand() -> Command {
 // Watch command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
    let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;

    let update_config = |book: &mut MDBook| {
        if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
@@ -41,7 +42,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {

    trigger_on_change(&book, |paths, book_dir| {
        info!("Files changed: {:?}\nBuilding book...\n", paths);
-        let result = MDBook::load(&book_dir).and_then(|mut b| {
+        let result = MDBook::load(book_dir).and_then(|mut b| {
            update_config(&mut b);
            b.build()
        });
@@ -62,14 +63,14 @@ fn remove_ignored_files(book_root: &Path, paths: &[PathBuf]) -> Vec<PathBuf> {

    match find_gitignore(book_root) {
        Some(gitignore_path) => {
-            match gitignore::File::new(gitignore_path.as_path()) {
-                Ok(exclusion_checker) => filter_ignored_files(exclusion_checker, paths),
-                Err(_) => {
-                    // We're unable to read the .gitignore file, so we'll silently allow everything.
-                    // Please see discussion: https://github.com/rust-lang/mdBook/pull/1051
-                    paths.iter().map(|path| path.to_path_buf()).collect()
-                }
+            let (ignore, err) = Gitignore::new(&gitignore_path);
+            if let Some(err) = err {
+                warn!(
+                    "error reading gitignore `{}`: {err}",
+                    gitignore_path.display()
+                );
            }
+            filter_ignored_files(ignore, paths)
        }
        None => {
            // There is no .gitignore file.
@@ -85,18 +86,13 @@ fn find_gitignore(book_root: &Path) -> Option<PathBuf> {
        .find(|p| p.exists())
 }

-fn filter_ignored_files(exclusion_checker: gitignore::File, paths: &[PathBuf]) -> Vec<PathBuf> {
+fn filter_ignored_files(ignore: Gitignore, paths: &[PathBuf]) -> Vec<PathBuf> {
    paths
        .iter()
-        .filter(|path| match exclusion_checker.is_excluded(path) {
-            Ok(exclude) => !exclude,
-            Err(error) => {
-                warn!(
-                    "Unable to determine if {:?} is excluded: {:?}. Including it.",
-                    &path, error
-                );
-                true
-            }
+        .filter(|path| {
+            !ignore
+                .matched_path_or_any_parents(path, path.is_dir())
+                .is_ignore()
        })
        .map(|path| path.to_path_buf())
        .collect()
@@ -134,11 +130,16 @@ where
    let _ = watcher.watch(&book.root.join("book.toml"), NonRecursive);

    for dir in &book.config.build.extra_watch_dirs {
-        let path = dir.canonicalize().unwrap();
-        if let Err(e) = watcher.watch(&path, Recursive) {
+        let path = book.root.join(dir);
+        let canonical_path = path.canonicalize().unwrap_or_else(|e| {
+            error!("Error while watching extra directory {path:?}:\n    {e}");
+            std::process::exit(1);
+        });
+
+        if let Err(e) = watcher.watch(&canonical_path, Recursive) {
            error!(
                "Error while watching extra directory {:?}:\n    {:?}",
-                path, e
+                canonical_path, e
            );
            std::process::exit(1);
        }
--- a/src/config.rs
+++ b/src/config.rs
@@ -308,7 +308,7 @@ impl<'de> serde::Deserialize<'de> for Config {
            warn!("`description` under a table called `[book]`, move the `destination` entry");
            warn!("from `[output.html]`, renamed to `build-dir`, under a table called");
            warn!("`[build]`, and it should all work.");
-            warn!("Documentation: http://rust-lang.github.io/mdBook/format/config.html");
+            warn!("Documentation: https://rust-lang.github.io/mdBook/format/config.html");
            return Ok(Config::from_legacy(raw));
        }

@@ -411,6 +411,9 @@ pub struct BookConfig {
    pub multilingual: bool,
    /// The main language of the book.
    pub language: Option<String>,
+    /// The direction of text in the book: Left-to-right (LTR) or Right-to-left (RTL).
+    /// When not specified, the text direction is derived from [`BookConfig::language`].
+    pub text_direction: Option<TextDirection>,
 }

 impl Default for BookConfig {
@@ -422,6 +425,43 @@ impl Default for BookConfig {
            src: PathBuf::from("src"),
            multilingual: false,
            language: Some(String::from("en")),
+            text_direction: None,
+        }
+    }
+}
+
+impl BookConfig {
+    /// Gets the realized text direction, either from [`BookConfig::text_direction`]
+    /// or derived from [`BookConfig::language`], to be used by templating engines.
+    pub fn realized_text_direction(&self) -> TextDirection {
+        if let Some(direction) = self.text_direction {
+            direction
+        } else {
+            TextDirection::from_lang_code(self.language.as_deref().unwrap_or_default())
+        }
+    }
+}
+
+/// Text direction to use for HTML output
+#[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
+pub enum TextDirection {
+    /// Left to right.
+    #[serde(rename = "ltr")]
+    LeftToRight,
+    /// Right to left
+    #[serde(rename = "rtl")]
+    RightToLeft,
+}
+
+impl TextDirection {
+    /// Gets the text direction from language code
+    pub fn from_lang_code(code: &str) -> Self {
+        match code {
+            // list sourced from here: https://github.com/abarrak/rtl/blob/master/lib/rtl/core.rb#L16
+            "ar" | "ara" | "arc" | "ae" | "ave" | "egy" | "he" | "heb" | "nqo" | "pal" | "phn"
+            | "sam" | "syc" | "syr" | "fa" | "per" | "fas" | "ku" | "kur" | "ur" | "urd"
+            | "pus" | "ps" | "yi" | "yid" => TextDirection::RightToLeft,
+            _ => TextDirection::LeftToRight,
        }
    }
 }
@@ -504,6 +544,8 @@ pub struct HtmlConfig {
    /// Playground settings.
    #[serde(alias = "playpen")]
    pub playground: Playground,
+    /// Code settings.
+    pub code: Code,
    /// Print settings.
    pub print: Print,
    /// Don't render section labels.
@@ -556,6 +598,7 @@ impl Default for HtmlConfig {
            additional_js: Vec::new(),
            fold: Fold::default(),
            playground: Playground::default(),
+            code: Code::default(),
            print: Print::default(),
            no_section_label: false,
            search: None,
@@ -642,6 +685,22 @@ impl Default for Playground {
    }
 }

+/// Configuration for tweaking how the the HTML renderer handles code blocks.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct Code {
+    /// A prefix string to hide lines per language (one or more chars).
+    pub hidelines: HashMap<String, String>,
+}
+
+impl Default for Code {
+    fn default() -> Code {
+        Code {
+            hidelines: HashMap::new(),
+        }
+    }
+}
+
 /// Configuration of the search functionality of the HTML renderer.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
@@ -703,7 +762,7 @@ trait Updateable<'de>: Serialize + Deserialize<'de> {
        let mut raw = Value::try_from(&self).expect("unreachable");

        if let Ok(value) = Value::try_from(value) {
-            let _ = raw.insert(key, value);
+            raw.insert(key, value);
        } else {
            return;
        }
@@ -769,6 +828,7 @@ mod tests {
            multilingual: true,
            src: PathBuf::from("source"),
            language: Some(String::from("ja")),
+            text_direction: None,
        };
        let build_should_be = BuildConfig {
            build_dir: PathBuf::from("outputs"),
@@ -1121,6 +1181,73 @@ mod tests {
        assert_eq!(&get_404_output_file(&html_config.input_404), "missing.html");
    }

+    #[test]
+    fn text_direction_ltr() {
+        let src = r#"
+        [book]
+        text-direction = "ltr"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, Some(TextDirection::LeftToRight));
+    }
+
+    #[test]
+    fn text_direction_rtl() {
+        let src = r#"
+        [book]
+        text-direction = "rtl"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, Some(TextDirection::RightToLeft));
+    }
+
+    #[test]
+    fn text_direction_none() {
+        let src = r#"
+        [book]
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, None);
+    }
+
+    #[test]
+    fn test_text_direction() {
+        let mut cfg = BookConfig::default();
+
+        // test deriving the text direction from language codes
+        cfg.language = Some("ar".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("he".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("en".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("ja".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        // test forced direction
+        cfg.language = Some("ar".into());
+        cfg.text_direction = Some(TextDirection::LeftToRight);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("ar".into());
+        cfg.text_direction = Some(TextDirection::RightToLeft);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("en".into());
+        cfg.text_direction = Some(TextDirection::LeftToRight);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("en".into());
+        cfg.text_direction = Some(TextDirection::RightToLeft);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+    }
+
    #[test]
    #[should_panic(expected = "Invalid configuration file")]
    fn invalid_language_type_error() {
--- a/src/preprocess/links.rs
+++ b/src/preprocess/links.rs
@@ -93,7 +93,7 @@ where
    for link in find_links(s) {
        replaced.push_str(&s[previous_end_index..link.start_index]);

-        match link.render_with_path(&path, chapter_title) {
+        match link.render_with_path(path, chapter_title) {
            Ok(new_content) => {
                if depth < MAX_LINK_NESTED_DEPTH {
                    if let Some(rel_path) = link.link_type.relative_path(path) {
@@ -327,7 +327,7 @@ impl<'a> Link<'a> {
        let base = base.as_ref();
        match self.link_type {
            // omit the escape char
-            LinkType::Escaped => Ok((&self.link_text[1..]).to_owned()),
+            LinkType::Escaped => Ok(self.link_text[1..].to_owned()),
            LinkType::Include(ref pat, ref range_or_anchor) => {
                let target = base.join(pat);

--- a/src/renderer/html_handlebars/hbs_renderer.rs
+++ b/src/renderer/html_handlebars/hbs_renderer.rs
@@ -1,5 +1,5 @@
 use crate::book::{Book, BookItem};
-use crate::config::{BookConfig, Config, HtmlConfig, Playground, RustEdition};
+use crate::config::{BookConfig, Code, Config, HtmlConfig, Playground, RustEdition};
 use crate::errors::*;
 use crate::renderer::html_handlebars::helpers;
 use crate::renderer::{RenderContext, Renderer};
@@ -99,7 +99,7 @@ impl HtmlHandlebars {
        ctx.data.insert("title".to_owned(), json!(title));
        ctx.data.insert(
            "path_to_root".to_owned(),
-            json!(utils::fs::path_to_root(&path)),
+            json!(utils::fs::path_to_root(path)),
        );
        if let Some(ref section) = ch.number {
            ctx.data
@@ -110,7 +110,12 @@ impl HtmlHandlebars {
        debug!("Render template");
        let rendered = ctx.handlebars.render("index", &ctx.data)?;

-        let rendered = self.post_process(rendered, &ctx.html_config.playground, ctx.edition);
+        let rendered = self.post_process(
+            rendered,
+            &ctx.html_config.playground,
+            &ctx.html_config.code,
+            ctx.edition,
+        );

        // Write to file
        debug!("Creating {}", filepath.display());
@@ -121,8 +126,12 @@ impl HtmlHandlebars {
            ctx.data.insert("path_to_root".to_owned(), json!(""));
            ctx.data.insert("is_index".to_owned(), json!(true));
            let rendered_index = ctx.handlebars.render("index", &ctx.data)?;
-            let rendered_index =
-                self.post_process(rendered_index, &ctx.html_config.playground, ctx.edition);
+            let rendered_index = self.post_process(
+                rendered_index,
+                &ctx.html_config.playground,
+                &ctx.html_config.code,
+                ctx.edition,
+            );
            debug!("Creating index.html from {}", ctx_path);
            utils::fs::write_file(&ctx.destination, "index.html", rendered_index.as_bytes())?;
        }
@@ -182,8 +191,12 @@ impl HtmlHandlebars {
        data_404.insert("title".to_owned(), json!(title));
        let rendered = handlebars.render("index", &data_404)?;

-        let rendered =
-            self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
+        let rendered = self.post_process(
+            rendered,
+            &html_config.playground,
+            &html_config.code,
+            ctx.config.rust.edition,
+        );
        let output_file = get_404_output_file(&html_config.input_404);
        utils::fs::write_file(destination, output_file, rendered.as_bytes())?;
        debug!("Creating 404.html ✓");
@@ -195,11 +208,13 @@ impl HtmlHandlebars {
        &self,
        rendered: String,
        playground_config: &Playground,
+        code_config: &Code,
        edition: Option<RustEdition>,
    ) -> String {
        let rendered = build_header_links(&rendered);
        let rendered = fix_code_blocks(&rendered);
        let rendered = add_playground_pre(&rendered, playground_config, edition);
+        let rendered = hide_lines(&rendered, code_config);

        rendered
    }
@@ -275,7 +290,8 @@ impl HtmlHandlebars {
            "FontAwesome/fonts/FontAwesome.ttf",
            theme::FONT_AWESOME_TTF,
        )?;
-        if html_config.copy_fonts {
+        // Don't copy the stock fonts if the user has specified their own fonts to use.
+        if html_config.copy_fonts && theme.fonts_css.is_none() {
            write_file(destination, "fonts/fonts.css", theme::fonts::CSS)?;
            for (file_name, contents) in theme::fonts::LICENSES.iter() {
                write_file(destination, file_name, contents)?;
@@ -291,20 +307,13 @@ impl HtmlHandlebars {
        }
        if let Some(fonts_css) = &theme.fonts_css {
            if !fonts_css.is_empty() {
-                if html_config.copy_fonts {
-                    warn!(
-                        "output.html.copy_fonts is deprecated.\n\
-                        Set copy_fonts=false and ensure the fonts you want are in \
-                        the `theme/fonts/` directory."
-                    );
-                }
-                write_file(destination, "fonts/fonts.css", &fonts_css)?;
+                write_file(destination, "fonts/fonts.css", fonts_css)?;
            }
        }
        if !html_config.copy_fonts && theme.fonts_css.is_none() {
            warn!(
-                "output.html.copy_fonts is deprecated.\n\
-                This book appears to have copy_fonts=false without a fonts.css file.\n\
+                "output.html.copy-fonts is deprecated.\n\
+                This book appears to have copy-fonts=false in book.toml without a fonts.css file.\n\
                Add an empty `theme/fonts/fonts.css` file to squelch this warning."
            );
        }
@@ -553,7 +562,7 @@ impl Renderer for HtmlHandlebars {
        // Print version
        let mut print_content = String::new();

-        fs::create_dir_all(&destination)
+        fs::create_dir_all(destination)
            .with_context(|| "Unexpected error when constructing destination path")?;

        let mut is_index = true;
@@ -589,8 +598,12 @@ impl Renderer for HtmlHandlebars {
            debug!("Render template");
            let rendered = handlebars.render("index", &data)?;

-            let rendered =
-                self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
+            let rendered = self.post_process(
+                rendered,
+                &html_config.playground,
+                &html_config.code,
+                ctx.config.rust.edition,
+            );

            utils::fs::write_file(destination, "print.html", rendered.as_bytes())?;
            debug!("Creating print.html ✓");
@@ -635,6 +648,10 @@ fn make_data(
        "language".to_owned(),
        json!(config.book.language.clone().unwrap_or_default()),
    );
+    data.insert(
+        "text_direction".to_owned(),
+        json!(config.book.realized_text_direction()),
+    );
    data.insert(
        "book_title".to_owned(),
        json!(config.book.title.clone().unwrap_or_default()),
@@ -795,8 +812,10 @@ fn make_data(
 /// Goes through the rendered HTML, making sure all header tags have
 /// an anchor respectively so people can link to sections directly.
 fn build_header_links(html: &str) -> String {
-    static BUILD_HEADER_LINKS: Lazy<Regex> =
-        Lazy::new(|| Regex::new(r"<h(\d)>(.*?)</h\d>").unwrap());
+    static BUILD_HEADER_LINKS: Lazy<Regex> = Lazy::new(|| {
+        Regex::new(r#"<h(\d)(?: id="([^"]+)")?(?: class="([^"]+)")?>(.*?)</h\d>"#).unwrap()
+    });
+    static IGNORE_CLASS: &[&str] = &["menu-title"];

    let mut id_counter = HashMap::new();

@@ -806,7 +825,22 @@ fn build_header_links(html: &str) -> String {
                .parse()
                .expect("Regex should ensure we only ever get numbers here");

-            insert_link_into_header(level, &caps[2], &mut id_counter)
+            // Ignore .menu-title because now it's getting detected by the regex.
+            if let Some(classes) = caps.get(3) {
+                for class in classes.as_str().split(" ") {
+                    if IGNORE_CLASS.contains(&class) {
+                        return caps[0].to_string();
+                    }
+                }
+            }
+
+            insert_link_into_header(
+                level,
+                &caps[4],
+                caps.get(2).map(|x| x.as_str().to_string()),
+                caps.get(3).map(|x| x.as_str().to_string()),
+                &mut id_counter,
+            )
        })
        .into_owned()
 }
@@ -816,15 +850,21 @@ fn build_header_links(html: &str) -> String {
 fn insert_link_into_header(
    level: usize,
    content: &str,
+    id: Option<String>,
+    classes: Option<String>,
    id_counter: &mut HashMap<String, usize>,
 ) -> String {
-    let id = utils::unique_id_from_content(content, id_counter);
+    let id = id.unwrap_or_else(|| utils::unique_id_from_content(content, id_counter));
+    let classes = classes
+        .map(|s| format!(" class=\"{s}\""))
+        .unwrap_or_default();

    format!(
-        r##"<h{level} id="{id}"><a class="header" href="#{id}">{text}</a></h{level}>"##,
+        r##"<h{level} id="{id}"{classes}><a class="header" href="#{id}">{text}</a></h{level}>"##,
        level = level,
        id = id,
-        text = content
+        text = content,
+        classes = classes
    )
 }

@@ -856,67 +896,64 @@ fn fix_code_blocks(html: &str) -> String {
        .into_owned()
 }

+static CODE_BLOCK_RE: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap());
+
 fn add_playground_pre(
    html: &str,
    playground_config: &Playground,
    edition: Option<RustEdition>,
 ) -> String {
-    static ADD_PLAYGROUND_PRE: Lazy<Regex> =
-        Lazy::new(|| Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap());
-
-    ADD_PLAYGROUND_PRE
+    CODE_BLOCK_RE
        .replace_all(html, |caps: &Captures<'_>| {
            let text = &caps[1];
            let classes = &caps[2];
            let code = &caps[3];

-            if classes.contains("language-rust") {
-                if (!classes.contains("ignore")
+            if classes.contains("language-rust")
+                && ((!classes.contains("ignore")
                    && !classes.contains("noplayground")
                    && !classes.contains("noplaypen")
                    && playground_config.runnable)
-                    || classes.contains("mdbook-runnable")
-                {
-                    let contains_e2015 = classes.contains("edition2015");
-                    let contains_e2018 = classes.contains("edition2018");
-                    let contains_e2021 = classes.contains("edition2021");
-                    let edition_class = if contains_e2015 || contains_e2018 || contains_e2021 {
-                        // the user forced edition, we should not overwrite it
-                        ""
-                    } else {
-                        match edition {
-                            Some(RustEdition::E2015) => " edition2015",
-                            Some(RustEdition::E2018) => " edition2018",
-                            Some(RustEdition::E2021) => " edition2021",
-                            None => "",
-                        }
-                    };
-
-                    // wrap the contents in an external pre block
-                    format!(
-                        "<pre class=\"playground\"><code class=\"{}{}\">{}</code></pre>",
-                        classes,
-                        edition_class,
-                        {
-                            let content: Cow<'_, str> = if playground_config.editable
-                                && classes.contains("editable")
-                                || text.contains("fn main")
-                                || text.contains("quick_main!")
-                            {
-                                code.into()
-                            } else {
-                                // we need to inject our own main
-                                let (attrs, code) = partition_source(code);
-
-                                format!("# #![allow(unused)]\n{}#fn main() {{\n{}#}}", attrs, code)
-                                    .into()
-                            };
-                            hide_lines(&content)
-                        }
-                    )
+                    || classes.contains("mdbook-runnable"))
+            {
+                let contains_e2015 = classes.contains("edition2015");
+                let contains_e2018 = classes.contains("edition2018");
+                let contains_e2021 = classes.contains("edition2021");
+                let edition_class = if contains_e2015 || contains_e2018 || contains_e2021 {
+                    // the user forced edition, we should not overwrite it
+                    ""
                } else {
-                    format!("<code class=\"{}\">{}</code>", classes, hide_lines(code))
-                }
+                    match edition {
+                        Some(RustEdition::E2015) => " edition2015",
+                        Some(RustEdition::E2018) => " edition2018",
+                        Some(RustEdition::E2021) => " edition2021",
+                        None => "",
+                    }
+                };
+
+                // wrap the contents in an external pre block
+                format!(
+                    "<pre class=\"playground\"><code class=\"{}{}\">{}</code></pre>",
+                    classes,
+                    edition_class,
+                    {
+                        let content: Cow<'_, str> = if playground_config.editable
+                            && classes.contains("editable")
+                            || text.contains("fn main")
+                            || text.contains("quick_main!")
+                        {
+                            code.into()
+                        } else {
+                            // we need to inject our own main
+                            let (attrs, code) = partition_source(code);
+
+                            format!("# #![allow(unused)]\n{}#fn main() {{\n{}#}}", attrs, code)
+                                .into()
+                        };
+                        content
+                    }
+                )
            } else {
                // not language-rust, so no-op
                text.to_owned()
@@ -925,7 +962,50 @@ fn add_playground_pre(
        .into_owned()
 }

-fn hide_lines(content: &str) -> String {
+/// Modifies all `<code>` blocks to convert "hidden" lines and to wrap them in
+/// a `<span class="boring">`.
+fn hide_lines(html: &str, code_config: &Code) -> String {
+    let language_regex = Regex::new(r"\blanguage-(\w+)\b").unwrap();
+    let hidelines_regex = Regex::new(r"\bhidelines=(\S+)").unwrap();
+    CODE_BLOCK_RE
+        .replace_all(html, |caps: &Captures<'_>| {
+            let text = &caps[1];
+            let classes = &caps[2];
+            let code = &caps[3];
+
+            if classes.contains("language-rust") {
+                format!(
+                    "<code class=\"{}\">{}</code>",
+                    classes,
+                    hide_lines_rust(code)
+                )
+            } else {
+                // First try to get the prefix from the code block
+                let hidelines_capture = hidelines_regex.captures(classes);
+                let hidelines_prefix = match &hidelines_capture {
+                    Some(capture) => Some(&capture[1]),
+                    None => {
+                        // Then look up the prefix by language
+                        language_regex.captures(classes).and_then(|capture| {
+                            code_config.hidelines.get(&capture[1]).map(|p| p.as_str())
+                        })
+                    }
+                };
+
+                match hidelines_prefix {
+                    Some(prefix) => format!(
+                        "<code class=\"{}\">{}</code>",
+                        classes,
+                        hide_lines_with_prefix(code, prefix)
+                    ),
+                    None => text.to_owned(),
+                }
+            }
+        })
+        .into_owned()
+}
+
+fn hide_lines_rust(content: &str) -> String {
    static BORING_LINES_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"^(\s*)#(.?)(.*)$").unwrap());

    let mut result = String::with_capacity(content.len());
@@ -958,6 +1038,26 @@ fn hide_lines(content: &str) -> String {
    result
 }

+fn hide_lines_with_prefix(content: &str, prefix: &str) -> String {
+    let mut result = String::with_capacity(content.len());
+    for line in content.lines() {
+        if line.trim_start().starts_with(prefix) {
+            let pos = line.find(prefix).unwrap();
+            let (ws, rest) = (&line[..pos], &line[pos + prefix.len()..]);
+
+            result += "<span class=\"boring\">";
+            result += ws;
+            result += rest;
+            result += "\n";
+            result += "</span>";
+            continue;
+        }
+        result += line;
+        result += "\n";
+    }
+    result
+}
+
 fn partition_source(s: &str) -> (String, String) {
    let mut after_header = false;
    let mut before = String::new();
@@ -992,7 +1092,10 @@ struct RenderItemContext<'a> {

 #[cfg(test)]
 mod tests {
+    use crate::config::TextDirection;
+
    use super::*;
+    use pretty_assertions::assert_eq;

    #[test]
    fn original_build_header_links() {
@@ -1021,6 +1124,21 @@ mod tests {
                "<h1>Foo</h1><h3>Foo</h3>",
                r##"<h1 id="foo"><a class="header" href="#foo">Foo</a></h1><h3 id="foo-1"><a class="header" href="#foo-1">Foo</a></h3>"##,
            ),
+            // id only
+            (
+                r##"<h1 id="foobar">Foo</h1>"##,
+                r##"<h1 id="foobar"><a class="header" href="#foobar">Foo</a></h1>"##,
+            ),
+            // class only
+            (
+                r##"<h1 class="class1 class2">Foo</h1>"##,
+                r##"<h1 id="foo" class="class1 class2"><a class="header" href="#foo">Foo</a></h1>"##,
+            ),
+            // both id and class
+            (
+                r##"<h1 id="foobar" class="class1 class2">Foo</h1>"##,
+                r##"<h1 id="foobar" class="class1 class2"><a class="header" href="#foobar">Foo</a></h1>"##,
+            ),
        ];

        for (src, should_be) in inputs {
@@ -1033,17 +1151,17 @@ mod tests {
    fn add_playground() {
        let inputs = [
          ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust\"><span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
          ("<code class=\"language-rust\">fn main() {}</code>",
           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>"),
          ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code></pre>"),
-          ("<code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code>",
           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>"),
+          ("<code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code></pre>"),
          ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code></pre>"),
          ("<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>",
-           "<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code>"),
+           "<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>"),
          ("<code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code>",
           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>"),
        ];
@@ -1063,7 +1181,7 @@ mod tests {
    fn add_playground_edition2015() {
        let inputs = [
          ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2015\"><span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
          ("<code class=\"language-rust\">fn main() {}</code>",
           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
          ("<code class=\"language-rust edition2015\">fn main() {}</code>",
@@ -1087,7 +1205,7 @@ mod tests {
    fn add_playground_edition2018() {
        let inputs = [
          ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2018\"><span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
          ("<code class=\"language-rust\">fn main() {}</code>",
           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
          ("<code class=\"language-rust edition2015\">fn main() {}</code>",
@@ -1111,7 +1229,7 @@ mod tests {
    fn add_playground_edition2021() {
        let inputs = [
            ("<code class=\"language-rust\">x()</code>",
-             "<pre class=\"playground\"><code class=\"language-rust edition2021\"><span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>"),
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
            ("<code class=\"language-rust\">fn main() {}</code>",
             "<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}</code></pre>"),
            ("<code class=\"language-rust edition2015\">fn main() {}</code>",
@@ -1131,4 +1249,66 @@ mod tests {
            assert_eq!(&*got, *should_be);
        }
    }
+
+    #[test]
+    fn hide_lines_language_rust() {
+        let inputs = [
+          (
+           "<pre class=\"playground\"><code class=\"language-rust\">\n# #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";</code></pre>",),
+          (
+           "<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>",
+           "<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>",),
+        ];
+        for (src, should_be) in &inputs {
+            let got = hide_lines(src, &Code::default());
+            assert_eq!(&*got, *should_be);
+        }
+    }
+
+    #[test]
+    fn hide_lines_language_other() {
+        let inputs = [
+          (
+           "<code class=\"language-python\">~hidden()\nnothidden():\n~    hidden()\n    ~hidden()\n    nothidden()</code>",
+           "<code class=\"language-python\"><span class=\"boring\">hidden()\n</span>nothidden():\n<span class=\"boring\">    hidden()\n</span><span class=\"boring\">    hidden()\n</span>    nothidden()\n</code>",),
+           (
+            "<code class=\"language-python hidelines=!!!\">!!!hidden()\nnothidden():\n!!!    hidden()\n    !!!hidden()\n    nothidden()</code>",
+            "<code class=\"language-python hidelines=!!!\"><span class=\"boring\">hidden()\n</span>nothidden():\n<span class=\"boring\">    hidden()\n</span><span class=\"boring\">    hidden()\n</span>    nothidden()\n</code>",),
+        ];
+        for (src, should_be) in &inputs {
+            let got = hide_lines(
+                src,
+                &Code {
+                    hidelines: {
+                        let mut map = HashMap::new();
+                        map.insert("python".to_string(), "~".to_string());
+                        map
+                    },
+                },
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
+
+    #[test]
+    fn test_json_direction() {
+        assert_eq!(json!(TextDirection::RightToLeft), json!("rtl"));
+        assert_eq!(json!(TextDirection::LeftToRight), json!("ltr"));
+    }
 }
--- a/src/renderer/html_handlebars/helpers/navigation.rs
+++ b/src/renderer/html_handlebars/helpers/navigation.rs
@@ -127,7 +127,7 @@ fn render(

    context.insert(
        "path_to_root".to_owned(),
-        json!(utils::fs::path_to_root(&base_path)),
+        json!(utils::fs::path_to_root(base_path)),
    );

    chapter
--- a/src/renderer/html_handlebars/search.rs
+++ b/src/renderer/html_handlebars/search.rs
@@ -138,9 +138,11 @@ fn render_item(

                in_heading = true;
            }
-            Event::End(Tag::Heading(i, ..)) if i as u32 <= max_section_depth => {
+            Event::End(Tag::Heading(i, id, _classes)) if i as u32 <= max_section_depth => {
                in_heading = false;
-                section_id = Some(utils::unique_id_from_content(&heading, &mut id_counter));
+                section_id = id
+                    .map(|id| id.to_string())
+                    .or_else(|| Some(utils::unique_id_from_content(&heading, &mut id_counter)));
                breadcrumbs.push(heading.clone());
            }
            Event::Start(Tag::FootnoteDefinition(name)) => {
--- a/src/renderer/markdown_renderer.rs
+++ b/src/renderer/markdown_renderer.rs
@@ -37,14 +37,14 @@ impl Renderer for MarkdownRenderer {
                if !ch.is_draft_chapter() {
                    utils::fs::write_file(
                        &ctx.destination,
-                        &ch.path.as_ref().expect("Checked path exists before"),
+                        ch.path.as_ref().expect("Checked path exists before"),
                        ch.content.as_bytes(),
                    )?;
                }
            }
        }

-        fs::create_dir_all(&destination)
+        fs::create_dir_all(destination)
            .with_context(|| "Unexpected error when constructing destination path")?;

        Ok(())
--- a/src/theme/book.js
+++ b/src/theme/book.js
@@ -68,7 +68,7 @@ function playground_text(playground, hidden = true) {
    }

    // updates the visibility of play button based on `no_run` class and
-    // used crates vs ones available on http://play.rust-lang.org
+    // used crates vs ones available on https://play.rust-lang.org
    function update_play_button(pre_block, playground_crates) {
        var play_button = pre_block.querySelector(".play-button");

@@ -179,7 +179,7 @@ function playground_text(playground, hidden = true) {
    // even if highlighting doesn't apply
    code_nodes.forEach(function (block) { block.classList.add('hljs'); });

-    Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
+    Array.from(document.querySelectorAll("code.hljs")).forEach(function (block) {

        var lines = Array.from(block.querySelectorAll('.boring'));
        // If no lines were hidden, return
@@ -346,7 +346,7 @@ function playground_text(playground, hidden = true) {
        }

        setTimeout(function () {
-            themeColorMetaTag.content = getComputedStyle(document.body).backgroundColor;
+            themeColorMetaTag.content = getComputedStyle(document.documentElement).backgroundColor;
        }, 1);

        if (window.ace && window.editors) {
@@ -441,7 +441,7 @@ function playground_text(playground, hidden = true) {
 })();

 (function sidebar() {
-    var html = document.querySelector("html");
+    var body = document.querySelector("body");
    var sidebar = document.getElementById("sidebar");
    var sidebarLinks = document.querySelectorAll('#sidebar a');
    var sidebarToggleButton = document.getElementById("sidebar-toggle");
@@ -449,8 +449,8 @@ function playground_text(playground, hidden = true) {
    var firstContact = null;

    function showSidebar() {
-        html.classList.remove('sidebar-hidden')
-        html.classList.add('sidebar-visible');
+        body.classList.remove('sidebar-hidden')
+        body.classList.add('sidebar-visible');
        Array.from(sidebarLinks).forEach(function (link) {
            link.setAttribute('tabIndex', 0);
        });
@@ -471,8 +471,8 @@ function playground_text(playground, hidden = true) {
    });

    function hideSidebar() {
-        html.classList.remove('sidebar-visible')
-        html.classList.add('sidebar-hidden');
+        body.classList.remove('sidebar-visible')
+        body.classList.add('sidebar-hidden');
        Array.from(sidebarLinks).forEach(function (link) {
            link.setAttribute('tabIndex', -1);
        });
@@ -483,14 +483,14 @@ function playground_text(playground, hidden = true) {

    // Toggle sidebar
    sidebarToggleButton.addEventListener('click', function sidebarToggle() {
-        if (html.classList.contains("sidebar-hidden")) {
+        if (body.classList.contains("sidebar-hidden")) {
            var current_width = parseInt(
                document.documentElement.style.getPropertyValue('--sidebar-width'), 10);
            if (current_width < 150) {
                document.documentElement.style.setProperty('--sidebar-width', '150px');
            }
            showSidebar();
-        } else if (html.classList.contains("sidebar-visible")) {
+        } else if (body.classList.contains("sidebar-visible")) {
            hideSidebar();
        } else {
            if (getComputedStyle(sidebar)['transform'] === 'none') {
@@ -506,14 +506,14 @@ function playground_text(playground, hidden = true) {
    function initResize(e) {
        window.addEventListener('mousemove', resize, false);
        window.addEventListener('mouseup', stopResize, false);
-        html.classList.add('sidebar-resizing');
+        body.classList.add('sidebar-resizing');
    }
    function resize(e) {
        var pos = (e.clientX - sidebar.offsetLeft);
        if (pos < 20) {
            hideSidebar();
        } else {
-            if (html.classList.contains("sidebar-hidden")) {
+            if (body.classList.contains("sidebar-hidden")) {
                showSidebar();
            }
            pos = Math.min(pos, window.innerWidth - 100);
@@ -522,7 +522,7 @@ function playground_text(playground, hidden = true) {
    }
    //on mouseup remove windows functions mousemove & mouseup
    function stopResize(e) {
-        html.classList.remove('sidebar-resizing');
+        body.classList.remove('sidebar-resizing');
        window.removeEventListener('mousemove', resize, false);
        window.removeEventListener('mouseup', stopResize, false);
    }
@@ -551,33 +551,41 @@ function playground_text(playground, hidden = true) {
            firstContact = null;
        }
    }, { passive: true });
-
-    // Scroll sidebar to current active section
-    var activeSection = document.getElementById("sidebar").querySelector(".active");
-    if (activeSection) {
-        // https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
-        activeSection.scrollIntoView({ block: 'center' });
-    }
 })();

 (function chapterNavigation() {
    document.addEventListener('keydown', function (e) {
        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
        if (window.search && window.search.hasFocus()) { return; }
+        var html = document.querySelector('html');

+        function next() {
+            var nextButton = document.querySelector('.nav-chapters.next');
+            if (nextButton) {
+                window.location.href = nextButton.href;
+            }
+        }
+        function prev() {
+            var previousButton = document.querySelector('.nav-chapters.previous');
+            if (previousButton) {
+                window.location.href = previousButton.href;
+            }
+        }
        switch (e.key) {
            case 'ArrowRight':
                e.preventDefault();
-                var nextButton = document.querySelector('.nav-chapters.next');
-                if (nextButton) {
-                    window.location.href = nextButton.href;
+                if (html.dir == 'rtl') {
+                    prev();
+                } else {
+                    next();
                }
                break;
            case 'ArrowLeft':
                e.preventDefault();
-                var previousButton = document.querySelector('.nav-chapters.previous');
-                if (previousButton) {
-                    window.location.href = previousButton.href;
+                if (html.dir == 'rtl') {
+                    next();
+                } else {
+                    prev();
                }
                break;
        }
@@ -676,13 +684,14 @@ function playground_text(playground, hidden = true) {
        }, { passive: true });
    })();
    (function controllBorder() {
-        menu.classList.remove('bordered');
-        document.addEventListener('scroll', function () {
+        function updateBorder() {
            if (menu.offsetTop === 0) {
                menu.classList.remove('bordered');
            } else {
                menu.classList.add('bordered');
            }
-        }, { passive: true });
+        }
+        updateBorder();
+        document.addEventListener('scroll', updateBorder, { passive: true });
    })();
 })();
--- a/src/theme/css/chrome.css
+++ b/src/theme/css/chrome.css
@@ -22,7 +22,7 @@ a > .hljs {
        the screen on small screens. Without it, dragging on mobile Safari
        will want to reposition the viewport in a weird way.
    */
-    overflow-x: hidden;
+    overflow-x: clip;
 }

 /* Menu Bar */
@@ -37,9 +37,9 @@ a > .hljs {
    display: flex;
    flex-wrap: wrap;
    background-color: var(--bg);
-    border-bottom-color: var(--bg);
-    border-bottom-width: 1px;
-    border-bottom-style: solid;
+    border-block-end-color: var(--bg);
+    border-block-end-width: 1px;
+    border-block-end-style: solid;
 }
 #menu-bar.sticky,
 .js #menu-bar-hover-placeholder:hover + #menu-bar,
@@ -56,7 +56,7 @@ a > .hljs {
    height: var(--menu-bar-height);
 }
 #menu-bar.bordered {
-    border-bottom-color: var(--table-border-color);
+    border-block-end-color: var(--table-border-color);
 }
 #menu-bar i, #menu-bar .icon-button {
    position: relative;
@@ -93,7 +93,7 @@ a > .hljs {
    display: flex;
    margin: 0 5px;
 }
-.no-js .left-buttons {
+.no-js .left-buttons button {
    display: none;
 }

@@ -160,7 +160,7 @@ a > .hljs {
 }

 .nav-wrapper {
-    margin-top: 50px;
+    margin-block-start: 50px;
    display: none;
 }

@@ -173,23 +173,34 @@ a > .hljs {
    background-color: var(--sidebar-bg);
 }

-.previous {
-    float: left;
-}
+/* Only Firefox supports flow-relative values */
+.previous { float: left; }
+[dir=rtl] .previous { float: right; }

+/* Only Firefox supports flow-relative values */
 .next {
    float: right;
    right: var(--page-padding);
 }
+[dir=rtl] .next {
+    float: left;
+    right: unset;
+    left: var(--page-padding);
+}
+
+/* Use the correct buttons for RTL layouts*/
+[dir=rtl] .previous i.fa-angle-left:before {content:"\f105";}
+[dir=rtl] .next i.fa-angle-right:before { content:"\f104"; }

@media only screen and (max-width: 1080px) {
    .nav-wide-wrapper { display: none; }
    .nav-wrapper { display: block; }
 }

+/* sidebar-visible */
@media only screen and (max-width: 1380px) {
-    .sidebar-visible .nav-wide-wrapper { display: none; }
-    .sidebar-visible .nav-wrapper { display: block; }
+    #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wide-wrapper { display: none; }
+    #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wrapper { display: block; }
 }

 /* Inline code */
@@ -236,7 +247,7 @@ pre > .buttons :hover {
    background-color: var(--theme-hover);
 }
 pre > .buttons i {
-    margin-left: 8px;
+    margin-inline-start: 8px;
 }
 pre > .buttons button {
    cursor: inherit;
@@ -273,7 +284,7 @@ pre > code {
 }

 pre > .result {
-    margin-top: 10px;
+    margin-block-start: 10px;
 }

 /* Search */
@@ -284,8 +295,14 @@ pre > .result {

 mark {
    border-radius: 2px;
-    padding: 0 3px 1px 3px;
-    margin: 0 -3px -1px -3px;
+    padding-block-start: 0;
+    padding-block-end: 1px;
+    padding-inline-start: 3px;
+    padding-inline-end: 3px;
+    margin-block-start: 0;
+    margin-block-end: -1px;
+    margin-inline-start: -3px;
+    margin-inline-end: -3px;
    background-color: var(--search-mark-bg);
    transition: background-color 300ms linear;
    cursor: pointer;
@@ -297,14 +314,17 @@ mark.fade-out {
 }

 .searchbar-outer {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
    max-width: var(--content-max-width);
 }

 #searchbar {
    width: 100%;
-    margin: 5px auto 0px auto;
+    margin-block-start: 5px;
+    margin-block-end: 0;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
    padding: 10px 16px;
    transition: box-shadow 300ms ease-in-out;
    border: 1px solid var(--searchbar-border-color);
@@ -320,20 +340,23 @@ mark.fade-out {
 .searchresults-header {
    font-weight: bold;
    font-size: 1em;
-    padding: 18px 0 0 5px;
+    padding-block-start: 18px;
+    padding-block-end: 0;
+    padding-inline-start: 5px;
+    padding-inline-end: 0;
    color: var(--searchresults-header-fg);
 }

 .searchresults-outer {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
    max-width: var(--content-max-width);
-    border-bottom: 1px dashed var(--searchresults-border-color);
+    border-block-end: 1px dashed var(--searchresults-border-color);
 }

 ul#searchresults {
    list-style: none;
-    padding-left: 20px;
+    padding-inline-start: 20px;
 }
 ul#searchresults li {
    margin: 10px 0px;
@@ -346,7 +369,10 @@ ul#searchresults li.focus {
 ul#searchresults span.teaser {
    display: block;
    clear: both;
-    margin: 5px 0 0 20px;
+    margin-block-start: 5px;
+    margin-block-end: 0;
+    margin-inline-start: 20px;
+    margin-inline-end: 0;
    font-size: 0.8em;
 }
 ul#searchresults span.teaser em {
@@ -369,12 +395,14 @@ ul#searchresults span.teaser em {
    background-color: var(--sidebar-bg);
    color: var(--sidebar-fg);
 }
+[dir=rtl] .sidebar { left: unset; right: 0; }
 .sidebar-resizing {
    -moz-user-select: none;
    -webkit-user-select: none;
    -ms-user-select: none;
    user-select: none;
 }
+.no-js .sidebar,
 .js:not(.sidebar-resizing) .sidebar {
    transition: transform 0.3s; /* Animation: slide away */
 }
@@ -398,12 +426,18 @@ ul#searchresults span.teaser em {
    top: 0;
    bottom: 0;
 }
+[dir=rtl] .sidebar .sidebar-resize-handle { right:  unset; left: 0; }
 .js .sidebar .sidebar-resize-handle {
    cursor: col-resize;
    width: 5px;
 }
-.sidebar-hidden .sidebar {
+/* sidebar-hidden */
+#sidebar-toggle-anchor:not(:checked) ~ .sidebar {
    transform: translateX(calc(0px - var(--sidebar-width)));
+    z-index: -1;
+}
+[dir=rtl] #sidebar-toggle-anchor:not(:checked) ~ .sidebar {
+    transform: translateX(var(--sidebar-width));
 }
 .sidebar::-webkit-scrollbar {
    background: var(--sidebar-bg);
@@ -412,19 +446,26 @@ ul#searchresults span.teaser em {
    background: var(--scrollbar);
 }

-.sidebar-visible .page-wrapper {
+/* sidebar-visible */
+#sidebar-toggle-anchor:checked ~ .page-wrapper {
    transform: translateX(var(--sidebar-width));
 }
+[dir=rtl] #sidebar-toggle-anchor:checked ~ .page-wrapper {
+    transform: translateX(calc(0px - var(--sidebar-width)));
+}
@media only screen and (min-width: 620px) {
-    .sidebar-visible .page-wrapper {
+    #sidebar-toggle-anchor:checked ~ .page-wrapper {
+        transform: none;
+        margin-inline-start: var(--sidebar-width);
+    }
+    [dir=rtl] #sidebar-toggle-anchor:checked ~ .page-wrapper {
        transform: none;
-        margin-left: var(--sidebar-width);
    }
 }

 .chapter {
    list-style: none outside none;
-    padding-left: 0;
+    padding-inline-start: 0;
    line-height: 2.2em;
 }

@@ -454,7 +495,7 @@ ul#searchresults span.teaser em {
 .chapter li > a.toggle {
    cursor: pointer;
    display: block;
-    margin-left: auto;
+    margin-inline-start: auto;
    padding: 0 10px;
    user-select: none;
    opacity: 0.68;
@@ -471,7 +512,7 @@ ul#searchresults span.teaser em {

 .chapter li.chapter-item {
    line-height: 1.5em;
-    margin-top: 0.6em;
+    margin-block-start: 0.6em;
 }

 .chapter li.expanded > a.toggle div {
@@ -494,7 +535,7 @@ ul#searchresults span.teaser em {

 .section {
    list-style: none outside none;
-    padding-left: 20px;
+    padding-inline-start: 20px;
    line-height: 1.9em;
 }

@@ -517,6 +558,7 @@ ul#searchresults span.teaser em {
    /* Don't let the children's background extend past the rounded corners. */
    overflow: hidden;
 }
+[dir=rtl] .theme-popup { left: unset;  right: 10px; }
 .theme-popup .default {
    color: var(--icons);
 }
@@ -527,7 +569,7 @@ ul#searchresults span.teaser em {
    padding: 2px 20px;
    line-height: 25px;
    white-space: nowrap;
-    text-align: left;
+    text-align: start;
    cursor: pointer;
    color: inherit;
    background: inherit;
@@ -540,6 +582,6 @@ ul#searchresults span.teaser em {
 .theme-selected::before {
    display: inline-block;
    content: "✓";
-    margin-left: -14px;
+    margin-inline-start: -14px;
    width: 14px;
 }
--- a/src/theme/css/general.css
+++ b/src/theme/css/general.css
@@ -5,6 +5,7 @@
 :root {
    /* Browser default font-size is 16px, this way 1 rem = 10px */
    font-size: 62.5%;
+    color-scheme: var(--color-scheme);
 }

 html {
@@ -24,6 +25,7 @@ body {
 code {
    font-family: var(--mono-font) !important;
    font-size: var(--code-font-size);
+    direction: ltr !important;
 }

 /* make long words/inline code not x overflow */
@@ -47,13 +49,13 @@ h1 code, h2 code, h3 code, h4 code, h5 code, h6 code {
 .hide-boring .boring { display: none; }
 .hidden { display: none !important; }

-h2, h3 { margin-top: 2.5em; }
-h4, h5 { margin-top: 2em; }
+h2, h3 { margin-block-start: 2.5em; }
+h4, h5 { margin-block-start: 2em; }

 .header + .header h3,
 .header + .header h4,
 .header + .header h5 {
-    margin-top: 1em;
+    margin-block-start: 1em;
 }

 h1:target::before,
@@ -64,7 +66,7 @@ h5:target::before,
 h6:target::before {
    display: inline-block;
    content: "»";
-    margin-left: -30px;
+    margin-inline-start: -30px;
    width: 30px;
 }

@@ -73,28 +75,34 @@ h6:target::before {
   https://bugs.webkit.org/show_bug.cgi?id=218076
 */
 :target {
+    /* Safari does not support logical properties */
    scroll-margin-top: calc(var(--menu-bar-height) + 0.5em);
 }

 .page {
    outline: 0;
    padding: 0 var(--page-padding);
-    margin-top: calc(0px - var(--menu-bar-height)); /* Compensate for the #menu-bar-hover-placeholder */
+    margin-block-start: calc(0px - var(--menu-bar-height)); /* Compensate for the #menu-bar-hover-placeholder */
 }
 .page-wrapper {
    box-sizing: border-box;
+    background-color: var(--bg);
 }
+.no-js .page-wrapper,
 .js:not(.sidebar-resizing) .page-wrapper {
    transition: margin-left 0.3s ease, transform 0.3s ease; /* Animation: slide away */
 }
+[dir=rtl] .js:not(.sidebar-resizing) .page-wrapper {
+    transition: margin-right 0.3s ease, transform 0.3s ease; /* Animation: slide away */
+}

 .content {
    overflow-y: auto;
    padding: 0 5px 50px 5px;
 }
 .content main {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
    max-width: var(--content-max-width);
 }
 .content p { line-height: 1.45em; }
@@ -144,8 +152,31 @@ blockquote {
    padding: 0 20px;
    color: var(--fg);
    background-color: var(--quote-bg);
-    border-top: .1em solid var(--quote-border);
-    border-bottom: .1em solid var(--quote-border);
+    border-block-start: .1em solid var(--quote-border);
+    border-block-end: .1em solid var(--quote-border);
+}
+
+.warning {
+    margin: 20px;
+    padding: 0 20px;
+    border-inline-start: 2px solid var(--warning-border);
+}
+
+.warning:before {
+    position: absolute;
+    width: 3rem;
+    height: 3rem;
+    margin-inline-start: calc(-1.5rem - 21px);
+    content: "ⓘ";
+    text-align: center;
+    background-color: var(--bg);
+    color: var(--warning-border);
+    font-weight: bold;
+    font-size: 2rem;
+}
+
+blockquote .warning:before {
+    background-color: var(--quote-bg);
 }

 kbd {
@@ -163,7 +194,7 @@ kbd {

 :not(.footnote-definition) + .footnote-definition,
 .footnote-definition + :not(.footnote-definition) {
-    margin-top: 2em;
+    margin-block-start: 2em;
 }
 .footnote-definition {
    font-size: 0.9em;
--- a/src/theme/css/print.css
+++ b/src/theme/css/print.css
@@ -8,7 +8,7 @@

 #page-wrapper.page-wrapper {
    transform: none;
-    margin-left: 0px;
+    margin-inline-start: 0px;
    overflow-y: initial;
 }

@@ -23,11 +23,7 @@
 }

 code {
-    background-color: #666666;
-    border-radius: 5px;
-
-    /* Force background to be printed in Chrome */
-    -webkit-print-color-adjust: exact;
+    direction: ltr !important;
 }

 pre > .buttons {
--- a/src/theme/css/variables.css
+++ b/src/theme/css/variables.css
@@ -38,6 +38,8 @@
    --quote-bg: hsl(226, 15%, 17%);
    --quote-border: hsl(226, 15%, 22%);

+    --warning-border: #ff8e00;
+
    --table-border-color: hsl(210, 25%, 13%);
    --table-header-bg: hsl(210, 25%, 28%);
    --table-alternate-bg: hsl(210, 25%, 11%);
@@ -50,6 +52,8 @@
    --searchresults-border-color: #888;
    --searchresults-li-bg: #252932;
    --search-mark-bg: #e3b171;
+
+    --color-scheme: dark;
 }

 .coal {
@@ -78,6 +82,8 @@
    --quote-bg: hsl(234, 21%, 18%);
    --quote-border: hsl(234, 21%, 23%);

+    --warning-border: #ff8e00;
+
    --table-border-color: hsl(200, 7%, 13%);
    --table-header-bg: hsl(200, 7%, 28%);
    --table-alternate-bg: hsl(200, 7%, 11%);
@@ -90,6 +96,8 @@
    --searchresults-border-color: #98a3ad;
    --searchresults-li-bg: #2b2b2f;
    --search-mark-bg: #355c7d;
+
+    --color-scheme: dark;
 }

 .light {
@@ -118,6 +126,8 @@
    --quote-bg: hsl(197, 37%, 96%);
    --quote-border: hsl(197, 37%, 91%);

+    --warning-border: #ff8e00;
+
    --table-border-color: hsl(0, 0%, 95%);
    --table-header-bg: hsl(0, 0%, 80%);
    --table-alternate-bg: hsl(0, 0%, 97%);
@@ -130,6 +140,8 @@
    --searchresults-border-color: #888;
    --searchresults-li-bg: #e4f2fe;
    --search-mark-bg: #a2cff5;
+
+    --color-scheme: light;
 }

 .navy {
@@ -158,6 +170,8 @@
    --quote-bg: hsl(226, 15%, 17%);
    --quote-border: hsl(226, 15%, 22%);

+    --warning-border: #ff8e00;
+
    --table-border-color: hsl(226, 23%, 16%);
    --table-header-bg: hsl(226, 23%, 31%);
    --table-alternate-bg: hsl(226, 23%, 14%);
@@ -170,6 +184,8 @@
    --searchresults-border-color: #5c5c68;
    --searchresults-li-bg: #242430;
    --search-mark-bg: #a2cff5;
+
+    --color-scheme: dark;
 }

 .rust {
@@ -198,6 +214,8 @@
    --quote-bg: hsl(60, 5%, 75%);
    --quote-border: hsl(60, 5%, 70%);

+    --warning-border: #ff8e00;
+
    --table-border-color: hsl(60, 9%, 82%);
    --table-header-bg: #b3a497;
    --table-alternate-bg: hsl(60, 9%, 84%);
@@ -210,6 +228,8 @@
    --searchresults-border-color: #888;
    --searchresults-li-bg: #dec2a2;
    --search-mark-bg: #e69f67;
+
+    --color-scheme: light;
 }

@media (prefers-color-scheme: dark) {
@@ -239,6 +259,8 @@
        --quote-bg: hsl(234, 21%, 18%);
        --quote-border: hsl(234, 21%, 23%);

+        --warning-border: #ff8e00;
+
        --table-border-color: hsl(200, 7%, 13%);
        --table-header-bg: hsl(200, 7%, 28%);
        --table-alternate-bg: hsl(200, 7%, 11%);
--- a/src/theme/index.hbs
+++ b/src/theme/index.hbs
@@ -1,11 +1,11 @@
 <!DOCTYPE HTML>
-<html lang="{{ language }}" class="sidebar-visible no-js {{ default_theme }}">
+<html lang="{{ language }}" class="{{ default_theme }}" dir="{{ text_direction }}">
    <head>
        <!-- Book generated using mdBook -->
        <meta charset="UTF-8">
        <title>{{ title }}</title>
        {{#if is_print }}
-        <meta name="robots" content="noindex" />
+        <meta name="robots" content="noindex">
        {{/if}}
        {{#if base_url}}
        <base href="{{ base_url }}">
@@ -17,7 +17,7 @@

        <meta name="description" content="{{ description }}">
        <meta name="viewport" content="width=device-width, initial-scale=1">
-        <meta name="theme-color" content="#ffffff" />
+        <meta name="theme-color" content="#ffffff">

        {{#if favicon_svg}}
        <link rel="icon" href="{{ path_to_root }}favicon.svg">
@@ -53,7 +53,7 @@
        <script async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
        {{/if}}
    </head>
-    <body>
+    <body class="sidebar-visible no-js">
    <div id="body-container">
        <!-- Provide site root to javascript -->
        <script>
@@ -83,22 +83,29 @@
            try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
            if (theme === null || theme === undefined) { theme = default_theme; }
            var html = document.querySelector('html');
-            html.classList.remove('no-js')
            html.classList.remove('{{ default_theme }}')
            html.classList.add(theme);
-            html.classList.add('js');
+            var body = document.querySelector('body');
+            body.classList.remove('no-js')
+            body.classList.add('js');
        </script>

+        <input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
+
        <!-- Hide / unhide sidebar before it is displayed -->
        <script>
-            var html = document.querySelector('html');
-            var sidebar = 'hidden';
+            var body = document.querySelector('body');
+            var sidebar = null;
+            var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
            if (document.body.clientWidth >= 1080) {
                try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
                sidebar = sidebar || 'visible';
+            } else {
+                sidebar = 'hidden';
            }
-            html.classList.remove('sidebar-visible');
-            html.classList.add("sidebar-" + sidebar);
+            sidebar_toggle.checked = sidebar === 'visible';
+            body.classList.remove('sidebar-visible');
+            body.classList.add("sidebar-" + sidebar);
        </script>

        <nav id="sidebar" class="sidebar" aria-label="Table of contents">
@@ -108,16 +115,38 @@
            <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
        </nav>

+        <!-- Track and set sidebar scroll position -->
+        <script>
+            var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
+            sidebarScrollbox.addEventListener('click', function(e) {
+                if (e.target.tagName === 'A') {
+                    sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
+                }
+            }, { passive: true });
+            var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
+            sessionStorage.removeItem('sidebar-scroll');
+            if (sidebarScrollTop) {
+                // preserve sidebar scroll position when navigating via links within sidebar
+                sidebarScrollbox.scrollTop = sidebarScrollTop;
+            } else {
+                // scroll sidebar to current active section when navigating via "next/previous chapter" buttons
+                var activeSection = document.querySelector('#sidebar .active');
+                if (activeSection) {
+                    activeSection.scrollIntoView({ block: 'center' });
+                }
+            }
+        </script>
+
        <div id="page-wrapper" class="page-wrapper">

            <div class="page">
                {{> header}}
                <div id="menu-bar-hover-placeholder"></div>
-                <div id="menu-bar" class="menu-bar sticky bordered">
+                <div id="menu-bar" class="menu-bar sticky">
                    <div class="left-buttons">
-                        <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                        <label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
                            <i class="fa fa-bars"></i>
-                        </button>
+                        </label>
                        <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
                            <i class="fa fa-paint-brush"></i>
                        </button>
@@ -193,7 +222,7 @@
                        {{/previous}}

                        {{#next}}
-                            <a rel="next" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                            <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                                <i class="fa fa-angle-right"></i>
                            </a>
                        {{/next}}
@@ -211,7 +240,7 @@
                {{/previous}}

                {{#next}}
-                    <a rel="next" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                    <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                        <i class="fa fa-angle-right"></i>
                    </a>
                {{/next}}
--- a/src/theme/tomorrow-night.css
+++ b/src/theme/tomorrow-night.css
@@ -1,7 +1,7 @@
 /* Tomorrow Night Theme */
-/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* https://github.com/jmblog/color-themes-for-highlightjs */
 /* Original theme - https://github.com/chriskempson/tomorrow-theme */
-/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* https://github.com/jmblog/color-themes-for-highlightjs */

 /* Tomorrow Comment */
 .hljs-comment {
--- a/src/utils/fs.rs
+++ b/src/utils/fs.rs
@@ -38,7 +38,6 @@ pub fn write_file<P: AsRef<Path>>(build_dir: &Path, filename: P, content: &[u8])
 /// Consider [submitting a new issue](https://github.com/rust-lang/mdBook/issues)
 /// or a [pull-request](https://github.com/rust-lang/mdBook/pulls) to improve it.
 pub fn path_to_root<P: Into<PathBuf>>(path: P) -> String {
-    debug!("path_to_root");
    // Remove filename and add "../" for every directory

    path.into()
@@ -167,7 +166,7 @@ pub fn copy_files_except_ext(
                        .expect("a file should have a file name...")
                )
            );
-            fs::copy(
+            copy(
                entry.path(),
                &to.join(
                    entry
@@ -181,6 +180,62 @@ pub fn copy_files_except_ext(
    Ok(())
 }

+/// Copies a file.
+fn copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> Result<()> {
+    let from = from.as_ref();
+    let to = to.as_ref();
+    return copy_inner(from, to)
+        .with_context(|| format!("failed to copy `{}` to `{}`", from.display(), to.display()));
+
+    // This is a workaround for an issue with the macOS file watcher.
+    // Rust's `std::fs::copy` function uses `fclonefileat`, which creates
+    // clones on APFS. Unfortunately fs events seem to trigger on both
+    // sides of the clone, and there doesn't seem to be a way to differentiate
+    // which side it is.
+    // https://github.com/notify-rs/notify/issues/465#issuecomment-1657261035
+    // contains more information.
+    //
+    // This is essentially a copy of the simple copy code path in Rust's
+    // standard library.
+    #[cfg(target_os = "macos")]
+    fn copy_inner(from: &Path, to: &Path) -> Result<()> {
+        use std::fs::OpenOptions;
+        use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
+
+        let mut reader = File::open(from)?;
+        let metadata = reader.metadata()?;
+        if !metadata.is_file() {
+            anyhow::bail!(
+                "expected a file, `{}` appears to be {:?}",
+                from.display(),
+                metadata.file_type()
+            );
+        }
+        let perm = metadata.permissions();
+        let mut writer = OpenOptions::new()
+            .mode(perm.mode())
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(to)?;
+        let writer_metadata = writer.metadata()?;
+        if writer_metadata.is_file() {
+            // Set the correct file permissions, in case the file already existed.
+            // Don't set the permissions on already existing non-files like
+            // pipes/FIFOs or device nodes.
+            writer.set_permissions(perm)?;
+        }
+        std::io::copy(&mut reader, &mut writer)?;
+        Ok(())
+    }
+
+    #[cfg(not(target_os = "macos"))]
+    fn copy_inner(from: &Path, to: &Path) -> Result<()> {
+        fs::copy(from, to)?;
+        Ok(())
+    }
+}
+
 pub fn get_404_output_file(input_404: &Option<String>) -> String {
    input_404
        .as_ref()
@@ -211,39 +266,36 @@ mod tests {
        };

        // Create a couple of files
-        if let Err(err) = fs::File::create(&tmp.path().join("file.txt")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.txt")) {
            panic!("Could not create file.txt: {}", err);
        }
-        if let Err(err) = fs::File::create(&tmp.path().join("file.md")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.md")) {
            panic!("Could not create file.md: {}", err);
        }
-        if let Err(err) = fs::File::create(&tmp.path().join("file.png")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.png")) {
            panic!("Could not create file.png: {}", err);
        }
-        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("sub_dir")) {
            panic!("Could not create sub_dir: {}", err);
        }
-        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir/file.png")) {
+        if let Err(err) = fs::File::create(tmp.path().join("sub_dir/file.png")) {
            panic!("Could not create sub_dir/file.png: {}", err);
        }
-        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir_exists")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("sub_dir_exists")) {
            panic!("Could not create sub_dir_exists: {}", err);
        }
-        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir_exists/file.txt")) {
+        if let Err(err) = fs::File::create(tmp.path().join("sub_dir_exists/file.txt")) {
            panic!("Could not create sub_dir_exists/file.txt: {}", err);
        }
-        if let Err(err) = symlink(
-            &tmp.path().join("file.png"),
-            &tmp.path().join("symlink.png"),
-        ) {
+        if let Err(err) = symlink(tmp.path().join("file.png"), tmp.path().join("symlink.png")) {
            panic!("Could not symlink file.png: {}", err);
        }

        // Create output dir
-        if let Err(err) = fs::create_dir(&tmp.path().join("output")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("output")) {
            panic!("Could not create output: {}", err);
        }
-        if let Err(err) = fs::create_dir(&tmp.path().join("output/sub_dir_exists")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("output/sub_dir_exists")) {
            panic!("Could not create output/sub_dir_exists: {}", err);
        }

@@ -254,22 +306,22 @@ mod tests {
        }

        // Check if the correct files where created
-        if !(&tmp.path().join("output/file.txt")).exists() {
+        if !tmp.path().join("output/file.txt").exists() {
            panic!("output/file.txt should exist")
        }
-        if (&tmp.path().join("output/file.md")).exists() {
+        if tmp.path().join("output/file.md").exists() {
            panic!("output/file.md should not exist")
        }
-        if !(&tmp.path().join("output/file.png")).exists() {
+        if !tmp.path().join("output/file.png").exists() {
            panic!("output/file.png should exist")
        }
-        if !(&tmp.path().join("output/sub_dir/file.png")).exists() {
+        if !tmp.path().join("output/sub_dir/file.png").exists() {
            panic!("output/sub_dir/file.png should exist")
        }
-        if !(&tmp.path().join("output/sub_dir_exists/file.txt")).exists() {
+        if !tmp.path().join("output/sub_dir_exists/file.txt").exists() {
            panic!("output/sub_dir/file.png should exist")
        }
-        if !(&tmp.path().join("output/symlink.png")).exists() {
+        if !tmp.path().join("output/symlink.png").exists() {
            panic!("output/symlink.png should exist")
        }
    }
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -183,6 +183,7 @@ pub fn new_cmark_parser(text: &str, curly_quotes: bool) -> Parser<'_, '_> {
    opts.insert(Options::ENABLE_FOOTNOTES);
    opts.insert(Options::ENABLE_STRIKETHROUGH);
    opts.insert(Options::ENABLE_TASKLISTS);
+    opts.insert(Options::ENABLE_HEADING_ATTRIBUTES);
    if curly_quotes {
        opts.insert(Options::ENABLE_SMART_PUNCTUATION);
    }
--- a/test_book/src/individual/code.md
+++ b/test_book/src/individual/code.md
@@ -10,7 +10,9 @@ This is a codeblock

 ---

-This line contains `inline code`
+This line contains `inline code` mixed with some other stuff. (LTR)
+
+ושורה זו מכילה `inline code` אבל עם טקסט בשפה שנכתבת מימין לשמאל. (RTL)

 ---

--- a/test_book/src/individual/heading.md
+++ b/test_book/src/individual/heading.md
@@ -13,3 +13,9 @@
 ##### Really Small Heading

 ###### Is it even a heading anymore - heading
+
+## Custom id {#example-id}
+
+## Custom class {.class1 .class2}
+
+## Both id and class {#example-id2 .class1 .class2}
--- a/test_book/src/individual/image.md
+++ b/test_book/src/individual/image.md
@@ -4,19 +4,19 @@ For copyright and trademark information on these images, please check [rust-artw

 ## A 16x16 image

-![16x16 rust-lang logo](http://rust-lang.org/logos/rust-logo-16x16.png)
+![16x16 rust-lang logo](https://rust-lang.org/logos/rust-logo-16x16.png)

 ## A 32x32 image

-![32x32 rust-lang logo](http://rust-lang.org/logos/rust-logo-32x32-blk.png)
+![32x32 rust-lang logo](https://rust-lang.org/logos/rust-logo-32x32-blk.png)

 ## A 256x256 image

-![256x256 rust-lang logo](http://rust-lang.org/logos/rust-logo-256x256.png)
+![256x256 rust-lang logo](https://rust-lang.org/logos/rust-logo-256x256.png)

 ## A 512x512 image

-![512x512 rust-lang logo](http://rust-lang.org/logos/rust-logo-512x512-blk.png)
+![512x512 rust-lang logo](https://rust-lang.org/logos/rust-logo-512x512-blk.png)

 ## A large image

--- a/test_book/src/individual/mixed.md
+++ b/test_book/src/individual/mixed.md
@@ -31,7 +31,7 @@ fn main(){

 A random image sprinkled in between

-![16x16 rust-lang logo](http://rust-lang.org/logos/rust-logo-16x16.png)
+![16x16 rust-lang logo](https://rust-lang.org/logos/rust-logo-16x16.png)

 ---

--- a/test_book/src/individual/strikethrough.md
+++ b/test_book/src/individual/strikethrough.md
@@ -1,5 +1,7 @@
 # Strikethrough

+~Single strike~
+
 ~~This is Striked~~

 ~~This is **strong**, _italic_ , **_both_** and striked~~
--- a/test_book/src/languages/highlight.md
+++ b/test_book/src/languages/highlight.md
@@ -57,7 +57,7 @@ _start:

 ## bash

-```
+```bash
 #!/bin/bash

 ###### CONFIG
--- a/tests/alternative_backends.rs
+++ b/tests/alternative_backends.rs
@@ -90,7 +90,7 @@ fn relative_command_path() {
            .set("output.html", toml::value::Table::new())
            .unwrap();
        config.set("output.myrenderer.command", cmd_path).unwrap();
-        let md = MDBook::init(&temp.path())
+        let md = MDBook::init(temp.path())
            .with_config(config)
            .build()
            .unwrap();
--- a/tests/cli/init.rs
+++ b/tests/cli/init.rs
@@ -0,0 +1,24 @@
+use crate::cli::cmd::mdbook_cmd;
+use crate::dummy_book::DummyBook;
+
+use mdbook::config::Config;
+
+/// Run `mdbook init` with `--force` to skip the confirmation prompts
+#[test]
+fn base_mdbook_init_can_skip_confirmation_prompts() {
+    let temp = DummyBook::new().build().unwrap();
+
+    // doesn't exist before
+    assert!(!temp.path().join("book").exists());
+
+    let mut cmd = mdbook_cmd();
+    cmd.args(["init", "--force"]).current_dir(temp.path());
+    cmd.assert()
+        .success()
+        .stdout(predicates::str::contains("\nAll done, no errors...\n"));
+
+    let config = Config::from_disk(temp.path().join("book.toml")).unwrap();
+    assert_eq!(config.book.title, None);
+
+    assert!(!temp.path().join(".gitignore").exists());
+}
--- a/tests/cli/mod.rs
+++ b/tests/cli/mod.rs
@@ -1,3 +1,4 @@
 mod build;
 mod cmd;
+mod init;
 mod test;
--- a/tests/dummy_book/mod.rs
+++ b/tests/dummy_book/mod.rs
@@ -112,12 +112,12 @@ fn recursive_copy<A: AsRef<Path>, B: AsRef<Path>>(from: A, to: B) -> Result<()>
    let from = from.as_ref();
    let to = to.as_ref();

-    for entry in WalkDir::new(&from) {
+    for entry in WalkDir::new(from) {
        let entry = entry.with_context(|| "Unable to inspect directory entry")?;

        let original_location = entry.path();
        let relative = original_location
-            .strip_prefix(&from)
+            .strip_prefix(from)
            .expect("`original_location` is inside the `from` directory");
        let new_location = to.join(relative);

@@ -126,7 +126,7 @@ fn recursive_copy<A: AsRef<Path>, B: AsRef<Path>>(from: A, to: B) -> Result<()>
                fs::create_dir_all(parent).with_context(|| "Couldn't create directory")?;
            }

-            fs::copy(&original_location, &new_location)
+            fs::copy(original_location, &new_location)
                .with_context(|| "Unable to copy file contents")?;
        }
    }
--- a/tests/dummy_book/src/SUMMARY.md
+++ b/tests/dummy_book/src/SUMMARY.md
@@ -14,6 +14,7 @@
    - [Unicode](first/unicode.md)
    - [No Headers](first/no-headers.md)
    - [Duplicate Headers](first/duplicate-headers.md)
+    - [Heading Attributes](first/heading-attributes.md)
 - [Second Chapter](second.md)
    - [Nested Chapter](second/nested.md)

--- a/tests/dummy_book/src/first/heading-attributes.md
+++ b/tests/dummy_book/src/first/heading-attributes.md
@@ -0,0 +1,5 @@
+# Heading Attributes {#attrs}
+
+## Heading with classes {.class1 .class2}
+
+## Heading with id and classes {#both .class1 .class2}
--- a/tests/rendered_output.rs
+++ b/tests/rendered_output.rs
@@ -35,6 +35,7 @@ const TOC_SECOND_LEVEL: &[&str] = &[
    "1.5. Unicode",
    "1.6. No Headers",
    "1.7. Duplicate Headers",
+    "1.8. Heading Attributes",
    "2.1. Nested Chapter",
 ];

@@ -275,7 +276,7 @@ fn root_index_html() -> Result<Document> {
        .with_context(|| "Book building failed")?;

    let index_page = temp.path().join("book").join("index.html");
-    let html = fs::read_to_string(&index_page).with_context(|| "Unable to read index.html")?;
+    let html = fs::read_to_string(index_page).with_context(|| "Unable to read index.html")?;

    Ok(Document::from(html.as_str()))
 }
@@ -412,7 +413,7 @@ fn recursive_includes_are_capped() {
    let content = &["Around the world, around the world
 Around the world, around the world
 Around the world, around the world"];
-    assert_contains_strings(&recursive, content);
+    assert_contains_strings(recursive, content);
 }

 #[test]
@@ -462,7 +463,7 @@ fn by_default_mdbook_use_index_preprocessor_to_convert_readme_to_index() {

    let second_index = temp.path().join("book").join("second").join("index.html");
    let unexpected_strings = vec!["Second README"];
-    assert_doesnt_contain_strings(&second_index, &unexpected_strings);
+    assert_doesnt_contain_strings(second_index, &unexpected_strings);
 }

 #[test]
@@ -628,10 +629,8 @@ fn edit_url_has_configured_src_dir_edit_url() {
 }

 fn remove_absolute_components(path: &Path) -> impl Iterator<Item = Component> + '_ {
-    path.components().skip_while(|c| match c {
-        Component::Prefix(_) | Component::RootDir => true,
-        _ => false,
-    })
+    path.components()
+        .skip_while(|c| matches!(c, Component::Prefix(_) | Component::RootDir))
 }

 /// Checks formatting of summary names with inline elements.
@@ -756,6 +755,7 @@ mod search {
        let no_headers = get_doc_ref("first/no-headers.html");
        let duplicate_headers_1 = get_doc_ref("first/duplicate-headers.html#header-text-1");
        let conclusion = get_doc_ref("conclusion.html#conclusion");
+        let heading_attrs = get_doc_ref("first/heading-attributes.html#both");

        let bodyidx = &index["index"]["index"]["body"]["root"];
        let textidx = &bodyidx["t"]["e"]["x"]["t"];
@@ -768,7 +768,7 @@ mod search {
        assert_eq!(docs[&some_section]["body"], "");
        assert_eq!(
            docs[&summary]["body"],
-            "Dummy Book Introduction First Chapter Nested Chapter Includes Recursive Markdown Unicode No Headers Duplicate Headers Second Chapter Nested Chapter Conclusion"
+            "Dummy Book Introduction First Chapter Nested Chapter Includes Recursive Markdown Unicode No Headers Duplicate Headers Heading Attributes Second Chapter Nested Chapter Conclusion"
        );
        assert_eq!(
            docs[&summary]["breadcrumbs"],
@@ -787,6 +787,10 @@ mod search {
            docs[&no_headers]["body"],
            "Capybara capybara capybara. Capybara capybara capybara. ThisLongWordIsIncludedSoWeCanCheckThatSufficientlyLongWordsAreOmittedFromTheSearchIndex."
        );
+        assert_eq!(
+            docs[&heading_attrs]["breadcrumbs"],
+            "First Chapter » Heading Attributes » Heading with id and classes"
+        );
    }

    // Setting this to `true` may cause issues with `cargo watch`,
@@ -803,7 +807,7 @@ mod search {
            let src = read_book_index(temp.path());

            let dest = Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/searchindex_fixture.json");
-            let dest = File::create(&dest).unwrap();
+            let dest = File::create(dest).unwrap();
            serde_json::to_writer_pretty(dest, &src).unwrap();

            src
@@ -891,8 +895,8 @@ fn custom_fonts() {
    assert_eq!(actual_files(&p.join("book/fonts")), &builtin_fonts);
    assert!(has_fonts_css(p));

-    // Mixed with copy_fonts=true
-    // This should generate a deprecation warning.
+    // Mixed with copy-fonts=true
+    // Should ignore the copy-fonts setting since the user has provided their own fonts.css.
    let temp = TempFileBuilder::new().prefix("mdbook").tempdir().unwrap();
    let p = temp.path();
    MDBook::init(p).build().unwrap();
@@ -900,10 +904,10 @@ fn custom_fonts() {
    write_file(&p.join("theme/fonts"), "myfont.woff", b"").unwrap();
    MDBook::load(p).unwrap().build().unwrap();
    assert!(has_fonts_css(p));
-    let mut expected = Vec::from(builtin_fonts);
-    expected.push("myfont.woff");
-    expected.sort();
-    assert_eq!(actual_files(&p.join("book/fonts")), expected.as_slice());
+    assert_eq!(
+        actual_files(&p.join("book/fonts")),
+        ["fonts.css", "myfont.woff"]
+    );

    // copy-fonts=false, no theme
    // This should generate a deprecation warning.
@@ -948,3 +952,19 @@ fn custom_fonts() {
        &["fonts.css", "myfont.woff"]
    );
 }
+
+#[test]
+fn custom_header_attributes() {
+    let temp = DummyBook::new().build().unwrap();
+    let md = MDBook::load(temp.path()).unwrap();
+    md.build().unwrap();
+
+    let contents = temp.path().join("book/first/heading-attributes.html");
+
+    let summary_strings = &[
+        r##"<h1 id="attrs"><a class="header" href="#attrs">Heading Attributes</a></h1>"##,
+        r##"<h2 id="heading-with-classes" class="class1 class2"><a class="header" href="#heading-with-classes">Heading with classes</a></h2>"##,
+        r##"<h2 id="both" class="class1 class2"><a class="header" href="#both">Heading with id and classes</a></h2>"##,
+    ];
+    assert_contains_strings(&contents, summary_strings);
+}
--- a/tests/searchindex_fixture.json
+++ b/tests/searchindex_fixture.json