Jeff King [off-list ref] writes:
If I understand Junio's suggestion correctly, it is very similar to how
"commit --author" works. See how it calls find_author_by_nickname(),
which finds the first commit matching the name, and then pulls out the
full name from format_commit_message().
Yup.
But I have to warn readers that it would not be a sane approach to
simply expose find_author_by_nickname() from builtin/commit.c as if
it is a generally reusable helper function. In a very limited
context of "git commit", what the helper does is OK to run a single
revision traversal without cleaning the parsed commit objects and
object flag bits after finding a single commit.
But generally, it would not be an approach that would scale (e.g. I
do not know if we can expect to be able to call the helper function
twice and get sensible results out of it).