$ git clone -n https://src.fedoraproject.org/rpms/mkvtoolnix.git /var/lib/mock/f41-build-59166005-6571410/root/chroot_tmpdir/scmroot/mkvtoolnix
Cloning into '/var/lib/mock/f41-build-59166005-6571410/root/chroot_tmpdir/scmroot/mkvtoolnix'...
$ git fetch origin 7d83f1937f18132ae5b249e35cd270990990e816:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mkvtoolnix
 * [new ref]         7d83f1937f18132ae5b249e35cd270990990e816 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7d83f19 update to 92.0 (resolves rhbz#2362454)