commitctx: document the manifest writing function...
commitctx: document the manifest writing function
Same spirit as for `_filecommit` lets document the input and output before
making any change or improvement.
This is part of a larger refactoring/cleanup of the commitctx code to clarify
and augment the logic gathering metadata useful for copy tracing. The current
code is a tad too long and entangled to make such update easy. We start with
easy and small cleanup.
Differential Revision:
https://phab.mercurial-scm.org/D8705
