$ git clone -n https://src.fedoraproject.org/rpms/mozilla-ublock-origin.git /var/lib/mock/f40-build-2200803-51789/root/chroot_tmpdir/scmroot/mozilla-ublock-origin
Cloning into '/var/lib/mock/f40-build-2200803-51789/root/chroot_tmpdir/scmroot/mozilla-ublock-origin'...
$ git fetch origin df6d4333f6cd33758ea62cc4935cfb656d842cb8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozilla-ublock-origin
 * [new ref]         df6d4333f6cd33758ea62cc4935cfb656d842cb8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at df6d433 Merge branch 'f38' into f39