$ git clone -n https://src.fedoraproject.org/rpms/gtk-v4l.git /var/lib/mock/f40-build-2236775-53519/root/chroot_tmpdir/scmroot/gtk-v4l
Cloning into '/var/lib/mock/f40-build-2236775-53519/root/chroot_tmpdir/scmroot/gtk-v4l'...
$ git fetch origin 647a0150219e5e865156664dcd9b7c5271ba85a5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gtk-v4l
 * [new ref]         647a0150219e5e865156664dcd9b7c5271ba85a5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 647a015 Fix C compatibility issues