This adds the ability to use multiple books for the GUI tests. This is
helpful since some tests need special configuration, and sharing the
same book can make it difficult or impossible to test different
configurations. It also makes it difficult to make changes to the
test_book since it can affect other tests.
This works by placing the books in the tests/gui/books directory. The
test runner will automatically build all the books. The gui tests can
then just access the DOC_PATH with the name of the book.
Books are now saved in a temp directory to make it easier to use the
DOC_PATH variable, instead of being tests/gui/books/book_name/book which
is a little awkward.
Following commits will restructure the existing book. This is just a
mechanical move.
This helps if you are creating new tests, or debugging existing tests by
allowing you to run `mdbook` directly in the test directory to try
things out. But we don't want to ever check these files in.
* Added support for gitignore files.
The watch command will now ignore files based on gitignore. This can be useful for when your editor creates cache or swap files.
* Ran cargo fmt.
* Made the code a bit tidier based on input from other Rust programmers.
Changed the type of the closure back to use PathBuf, not &PathBuf.
Reduced nesting.
