$ git clone -n https://src.fedoraproject.org/rpms/xrootd-s3-http.git /var/lib/mock/f42-build-863059-171350/root/chroot_tmpdir/scmroot/xrootd-s3-http
Cloning into '/var/lib/mock/f42-build-863059-171350/root/chroot_tmpdir/scmroot/xrootd-s3-http'...
$ git fetch origin e2fbb327bf72ce9412b9babc80d83e05dd66bc66:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xrootd-s3-http
 * [new ref]         e2fbb327bf72ce9412b9babc80d83e05dd66bc66 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e2fbb32 rebuild for tinyxml2