$ git clone -n https://src.fedoraproject.org/rpms/ffmpeg.git /var/lib/mock/f40-build-740292-109618/root/chroot_tmpdir/scmroot/ffmpeg
Cloning into '/var/lib/mock/f40-build-740292-109618/root/chroot_tmpdir/scmroot/ffmpeg'...
$ git fetch origin b3cfba90d45ccf7fdd58a4e0fa79e6527890b58d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ffmpeg
 * [new ref]         b3cfba90d45ccf7fdd58a4e0fa79e6527890b58d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b3cfba9 Update to 6.0.1