$ git clone -n https://src.fedoraproject.org/rpms/R-xml2.git /var/lib/mock/f40-build-2164108-50969/root/chroot_tmpdir/scmroot/R-xml2
Cloning into '/var/lib/mock/f40-build-2164108-50969/root/chroot_tmpdir/scmroot/R-xml2'...
$ git fetch origin b51a0f8949b3c6ee04cc9dba92b9099cfc3e99e5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-xml2
 * [new ref]         b51a0f8949b3c6ee04cc9dba92b9099cfc3e99e5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b51a0f8 Fix building against libxml2 2.12.0