$ git clone -n https://src.fedoraproject.org/rpms/mozilla-ublock-origin.git /var/lib/mock/f38-build-side-42-init-devel-1066181-29775/root/chroot_tmpdir/scmroot/mozilla-ublock-origin
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1066181-29775/root/chroot_tmpdir/scmroot/mozilla-ublock-origin'...
$ git fetch origin 396588bfa76126d931ec5c0ad9a2edd60b9c6d3b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozilla-ublock-origin
 * [new ref]         396588bfa76126d931ec5c0ad9a2edd60b9c6d3b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 396588b Merge branch 'f37' into f38