$ git clone -n https://src.fedoraproject.org/rpms/percolator.git /var/lib/mock/f42-build-862903-171231/root/chroot_tmpdir/scmroot/percolator
Cloning into '/var/lib/mock/f42-build-862903-171231/root/chroot_tmpdir/scmroot/percolator'...
$ git fetch origin 923035615c35617553930ae0df3a202140c9fa95:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/percolator
 * [new ref]         923035615c35617553930ae0df3a202140c9fa95 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9230356 Rebuild for xerces-c 3.3