$ git clone -n https://src.fedoraproject.org/rpms/mozjs102.git /var/lib/mock/f39-build-2082172-49816/root/chroot_tmpdir/scmroot/mozjs102
Cloning into '/var/lib/mock/f39-build-2082172-49816/root/chroot_tmpdir/scmroot/mozjs102'...
$ git fetch origin d7fe251f060db8d55a5a1379768ff10285a78cb6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs102
 * [new ref]         d7fe251f060db8d55a5a1379768ff10285a78cb6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d7fe251 mozjs102-102.15.1 (last release)