$ git clone -n https://src.fedoraproject.org/rpms/image-builder.git /var/lib/mock/f42-build-side-1-3588167-46943/root/chroot_tmpdir/scmroot/image-builder
Cloning into '/var/lib/mock/f42-build-side-1-3588167-46943/root/chroot_tmpdir/scmroot/image-builder'...
$ git fetch origin 5e63bdd4a44734e5688ae8d21a76151c894b061c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/image-builder
 * [new ref]         5e63bdd4a44734e5688ae8d21a76151c894b061c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5e63bdd Update to 22 upstream release