$ git clone -n https://src.fedoraproject.org/rpms/mozilla-ublock-origin.git /var/lib/mock/f38-build-side-42-init-devel-1179251-30617/root/chroot_tmpdir/scmroot/mozilla-ublock-origin
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1179251-30617/root/chroot_tmpdir/scmroot/mozilla-ublock-origin'...
$ git fetch origin e2e4c6412074d31f7d0def5b3a59d7aedabc64ff:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozilla-ublock-origin
 * [new ref]         e2e4c6412074d31f7d0def5b3a59d7aedabc64ff -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e2e4c64 Merge branch 'f37' into f38