$ git clone -n https://src.fedoraproject.org/rpms/mozjs115.git /var/lib/mock/f39-build-1996620-43957/root/chroot_tmpdir/scmroot/mozjs115
Cloning into '/var/lib/mock/f39-build-1996620-43957/root/chroot_tmpdir/scmroot/mozjs115'...
$ git fetch origin 0bec774217b3226a848f1df150e9d23d83c7c23c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs115
 * [new ref]         0bec774217b3226a848f1df150e9d23d83c7c23c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0bec774 mozjs115-115.4.0