Preprocessors using `pulldown-cmark-to-cmark` do not yet perform round
trips 100% correctly, and insert leading spaces and an extra initial `>`
for block quotes, so strip those. Once that is fixed upstream, this will
become a no-op, and can be removed then.
- Create an `mdbook_trpl` library package which hosts shared concerns
for the packages, e.g. error and config handling.
- Move `mdbook-trpl-note` and `mdbook-trpl-listing` into the new shared
package, with binaries at `src/bin/(note|listing)/main.rs` and the
existing libraries at `src/note/mod.rs` and `src/listing/mod.rs` with
their associated tests.
- Extract their actual shared pieces into the crate root.
- Update `tools/nostarch.sh` to build all the bins in `mdbook_trpl` at
one time.
At the moment, this doesn't do a lot except trim down the number of
packages in the repository, but it sets things up nicely to support more
preprocessors (which I am going to add shortly).
- Update the `tools/nostarch` script to `cargo install` each of the
preprocessors so they are always available to run and do not require
any manual intervention.
- Add support for `"markdown"` renderer in the preprocessors.
Introduce a `book.toml` in the `nostarch` directory, which matches the
existing `book.toml` except for specifying the correct relative input
and output directories and disabling the `trpl-note` preprocessor. This
also lets us simplify the invocation in the `nostarch.sh` script a bit,
by providing the configuration directly in the file.
