* Link out to FAQ for an introduction to rewriting history.
* Link out to our commit message formatting guidelines.
* Expand a bit more on what it means to tidy commit history.
This improves upon the existing documentation to provide a clearer end-to-end
workflow for new contributors and people who wish to build the toolchain
locally but do not intend to submit patches.
We also provide more directions for systematically utilizing our existing
documentation.