$ git clone -n https://src.fedoraproject.org/rpms/gjs.git /var/lib/mock/f42-build-3340354-44984/root/chroot_tmpdir/scmroot/gjs
Cloning into '/var/lib/mock/f42-build-3340354-44984/root/chroot_tmpdir/scmroot/gjs'...
$ git fetch origin 138b416f36f88c4ea9365e367ec94c3ecf8a724a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gjs
 * [new ref]         138b416f36f88c4ea9365e367ec94c3ecf8a724a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 138b416 Update to 1.83.90