$ git clone -n https://src.fedoraproject.org/rpms/mozjs128.git /var/lib/mock/f41-build-848002-164378/root/chroot_tmpdir/scmroot/mozjs128
Cloning into '/var/lib/mock/f41-build-848002-164378/root/chroot_tmpdir/scmroot/mozjs128'...
$ git fetch origin 05e6b0abd247699d3807a8046e7af7018c96cb79:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs128
 * [new ref]         05e6b0abd247699d3807a8046e7af7018c96cb79 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 05e6b0a mozjs128-128.2.0 (RHBZ#)