config: respect '~' and '~user' in mailmap.file
config: respect '~' and '~user' in mailmap.file

git_config_string() does not handle '~' and '~user' as part of the
value. Using git_config_pathname() fixes this.

Signed-off-by: Øystein Walle <9b766412a36388a47066e0b9bbedb19c44c5d1df@gmail.com>
Reviewed-by: Jeff King <696e3fbcf235d40b6ea1ebd61c87cbea79d444e7@peff.net>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git