$ git clone -n https://src.fedoraproject.org/rpms/mkvtoolnix.git /var/lib/mock/f41-build-1273149-23132/root/chroot_tmpdir/scmroot/mkvtoolnix
Cloning into '/var/lib/mock/f41-build-1273149-23132/root/chroot_tmpdir/scmroot/mkvtoolnix'...
$ git fetch origin b0d96387c74f9f079fec41559599bcbf1e910dac:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mkvtoolnix
 * [new ref]         b0d96387c74f9f079fec41559599bcbf1e910dac -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b0d9638 Merge branch 'f40' into rawhide