Merge branch 'mg/commit-author-no-match-malformed-message'

The error message from "git commit", when a non-existing author
name was given as value to the "--author=" parameter, has been
reworded to avoid misunderstanding.

* mg/commit-author-no-match-malformed-message:
commit: reword --author error message

diff --cc builtin/commit.c
Simple merge