$ git clone -n https://src.fedoraproject.org/rpms/mozjs128.git /var/lib/mock/f41-build-845998-162905/root/chroot_tmpdir/scmroot/mozjs128
Cloning into '/var/lib/mock/f41-build-845998-162905/root/chroot_tmpdir/scmroot/mozjs128'...
$ git fetch origin 1c007690e29103fda22c88c6eaf878e4b2980f63:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs128
 * [new ref]         1c007690e29103fda22c88c6eaf878e4b2980f63 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1c00769 Init