$ git clone -n https://src.fedoraproject.org/rpms/mkvtoolnix.git /var/lib/mock/f40-build-2613387-64066/root/chroot_tmpdir/scmroot/mkvtoolnix
Cloning into '/var/lib/mock/f40-build-2613387-64066/root/chroot_tmpdir/scmroot/mkvtoolnix'...
$ git fetch origin 8d7fae3c054035a5fc17265a4d4e9269f191a5d8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mkvtoolnix
 * [new ref]         8d7fae3c054035a5fc17265a4d4e9269f191a5d8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8d7fae3 Merge branch 'f39' into f40