$ git clone -n https://src.fedoraproject.org/rpms/perl-Mail-Message.git /var/lib/mock/f40-build-2239279-53610/root/chroot_tmpdir/scmroot/perl-Mail-Message
Cloning into '/var/lib/mock/f40-build-2239279-53610/root/chroot_tmpdir/scmroot/perl-Mail-Message'...
$ git fetch origin c0df694a2f05368d43b2903c6125f0d46730a624:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Mail-Message
 * [new ref]         c0df694a2f05368d43b2903c6125f0d46730a624 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c0df694 Update to 3.015 (rhbz#2253976)