$ git clone -n https://src.fedoraproject.org/rpms/mozjs115.git /var/lib/mock/f39-build-1572654-37788/root/chroot_tmpdir/scmroot/mozjs115
Cloning into '/var/lib/mock/f39-build-1572654-37788/root/chroot_tmpdir/scmroot/mozjs115'...
$ git fetch origin bf16db469e36777db155daf9e02de7e3bb2e2d8a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs115
 * [new ref]         bf16db469e36777db155daf9e02de7e3bb2e2d8a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bf16db4 mozjs115-115.3.1