> This can be in a general Mercurial section before the section specific
> to committers, or else spread throughout (e.g. in the FAQ).

FWIW I'm leaning towards making the committing.rst page for committers only, and move general instructions for non-committers elsewhere.  For this issue I think it might be OK to either add a FAQ about Rietveld that also mentions the git format, or possibly include it in a new "Rietveld" section somewhere in the tracker docs (see #13963).