Merge branch 'ap/commit-author-mailmap'

"git commit --author=$name", when $name is not in the canonical
"A. U. Thor <au.thor@example.xz>" format, looks for a matching name
from existing history, but did not consult mailmap to grab the
preferred author name.

* ap/commit-author-mailmap:
commit: search author pattern against mailmap

diff --cc builtin/commit.c
Simple merge

diff --cc t/t4203-mailmap.sh
Simple merge