$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rugged.git /var/lib/mock/f41-build-859047-168539/root/chroot_tmpdir/scmroot/rubygem-rugged
Cloning into '/var/lib/mock/f41-build-859047-168539/root/chroot_tmpdir/scmroot/rubygem-rugged'...
$ git fetch origin 89853acd84108b98ac2485e7809a1c155301435a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rugged
 * [new ref]         89853acd84108b98ac2485e7809a1c155301435a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 89853ac Rebuild for libgit2 1.8.x