$ git clone -n https://src.fedoraproject.org/rpms/ffmpeg.git /var/lib/mock/f40-build-774009-127559/root/chroot_tmpdir/scmroot/ffmpeg
Cloning into '/var/lib/mock/f40-build-774009-127559/root/chroot_tmpdir/scmroot/ffmpeg'...
$ git fetch origin e4f0babc7962e35cae66e2dac6df00091b73013e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ffmpeg
 * [new ref]         e4f0babc7962e35cae66e2dac6df00091b73013e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e4f0bab Rebuild for dav1d 1.3.0