From the [pull request comment][pr], here's a rough summary of what
was done in the squashed commits.
---
\# Summary Parser
- Added a private submodule called `mdbook::loader::summary` which
contains all the code for parsing `SUMMARY.md`
- A `Summary` contains a title (optional), then some prefix, numbered,
and suffix chapters (technically `Vec<SummaryItem>`)
- A `SummaryItem` is either a `Link` (i.e. link to a chapter), or a
separator
- A `Link` contains the chapter name, its location relative to the
book's `src/` directory, and a list of nested `SummaryItems`
- The `SummaryParser` (a state machine-based parser) uses
`pulldown_cmark` to turn the `SUMMARY.md` string into a stream of
`Events`, it then iterates over those events changing its behaviour
depending on the current state,
- The states are `Start`, `PrefixChapters`, `NestedChapters(u32)` (the
`u32` represents your nesting level, because lists can contain lists),
`SuffixChapters`, and `End`
- Each state will read the appropriate link and build up the
`Summary`, skipping any events which aren't a link, horizontal rule
(separator), or a list
\# Loader
- Created a basic loader which can be used to load the `SUMMARY.md` in
a directory.
\# Tests
- Added a couple unit tests for each state in the parser's state
machine
- Added integration tests for parsing a dummy SUMMARY.md then asserting
the result is exactly what we expected
[pr]: https://github.com/azerupi/mdBook/pull/371#issuecomment-312636102
Michael Bryan