$ git clone -n https://src.fedoraproject.org/rpms/appstream.git /var/lib/mock/f40-build-788871-135454/root/chroot_tmpdir/scmroot/appstream
Cloning into '/var/lib/mock/f40-build-788871-135454/root/chroot_tmpdir/scmroot/appstream'...
$ git fetch origin cbd2eb94db83d3f8cc9daf12c8c1563235510b40:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/appstream
 * [new ref]         cbd2eb94db83d3f8cc9daf12c8c1563235510b40 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cbd2eb9 Update to 1.0.2