$ git clone -n https://src.fedoraproject.org/rpms/R-gert.git /var/lib/mock/f40-build-2206953-52070/root/chroot_tmpdir/scmroot/R-gert
Cloning into '/var/lib/mock/f40-build-2206953-52070/root/chroot_tmpdir/scmroot/R-gert'...
$ git fetch origin 261e79c27055fa8c143b4e8287103320122294c7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gert
 * [new ref]         261e79c27055fa8c143b4e8287103320122294c7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 261e79c Rebuild for libgit2 1.7.x