add a few more docs to existing funcs

Change-Id: I27317a59aba67c05ca1fd333e8f064c0edccb209
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/343185


Reviewed-by: LaMont Jones <lamontjones@google.com>
Tested-by: Mike Frysinger <vapier@google.com>