$ git clone -n https://src.fedoraproject.org/rpms/xerces-j2.git /var/lib/mock/f42-build-3364913-45045/root/chroot_tmpdir/scmroot/xerces-j2
Cloning into '/var/lib/mock/f42-build-3364913-45045/root/chroot_tmpdir/scmroot/xerces-j2'...
$ git fetch origin 39e4b5bafa4a140224edf8c817c4c917464039fc:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xerces-j2
 * [new ref]         39e4b5bafa4a140224edf8c817c4c917464039fc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 39e4b5b Remove javadoc subpackage