$ git clone -n https://src.fedoraproject.org/rpms/mpv.git /var/lib/mock/f39-build-1765820-41501/root/chroot_tmpdir/scmroot/mpv
Cloning into '/var/lib/mock/f39-build-1765820-41501/root/chroot_tmpdir/scmroot/mpv'...
$ git fetch origin 3c026eb0f8add8674f372ec8502012304a502746:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mpv
 * [new ref]         3c026eb0f8add8674f372ec8502012304a502746 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3c026eb Rebuilt