$ git clone -n https://src.fedoraproject.org/rpms/gstreamer1.git /var/lib/mock/f42-build-side-1-3584226-46892/root/chroot_tmpdir/scmroot/gstreamer1
Cloning into '/var/lib/mock/f42-build-side-1-3584226-46892/root/chroot_tmpdir/scmroot/gstreamer1'...
$ git fetch origin 121db838a96354d543efa850710f3bea962586f9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gstreamer1
 * [new ref]         121db838a96354d543efa850710f3bea962586f9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 121db83 1.26.3