$ git clone -n https://src.fedoraproject.org/rpms/gcr.git /var/lib/mock/f40-build-789046-135500/root/chroot_tmpdir/scmroot/gcr
Cloning into '/var/lib/mock/f40-build-789046-135500/root/chroot_tmpdir/scmroot/gcr'...
$ git fetch origin 416dfb9339a4218399851349d3a6e373a811256a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcr
 * [new ref]         416dfb9339a4218399851349d3a6e373a811256a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 416dfb9 Update to 4.2.0