$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rdoc.git /var/lib/mock/f41-build-746371-13355/root/chroot_tmpdir/scmroot/rubygem-rdoc
Cloning into '/var/lib/mock/f41-build-746371-13355/root/chroot_tmpdir/scmroot/rubygem-rdoc'...
$ git fetch origin ddb95774de4af2afdf8fc9c970d14e67e8d2584a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rdoc
 * [new ref]         ddb95774de4af2afdf8fc9c970d14e67e8d2584a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ddb9577 Eliminate use of obsolete %patchN syntax (#2283636)