message: Add "Updating tools" section to toolstate chapter
diff: @@ -50,6 +50,17 @@ break.
  For further details, see the comments in the involved files: [`checktools.sh`],
  [`publish_toolstate.py`] as well as the other files mentioned there.
  +## Updating tools
  +
  +Tools can be updated by updating the submodule to the proper commit.
  +
  +Run `git submodule update --remote path/to/submodule`, add the updates, make
  +sure the tests pass, commit, and send a pull request. The path is from the
  +root of the rust repository, so for example, the reference is
  +`src/doc/reference` and rustfmt is `src/tools/rustfmt`.
  +
  +While not required, [subup] may assist you with this.
  +
  ## Adding a tool
  To add a new tool to be tracked, the following steps must be taken:
  @@ -77,6 +88,7 @@ To add a new tool to be tracked, the following steps must be taken:
  [`latest.json`]: https://github.com/rust-lang-nursery/rust-toolstate/blob/master/_data/latest.json
  [Book]: https://doc.rust-lang.org/book/
  [Reference]: https://doc.rust-lang.org/reference/
  +[subup]: https://github.com/ehuss/subup
  [toolstate]: https://rust-lang-nursery.github.io/rust-toolstate/
  [toolstate repository]: https://github.com/rust-lang-nursery/rust-toolstate/
  [forge]: ../index.html
  