$ git clone -n https://src.fedoraproject.org/rpms/ostree.git /var/lib/mock/f40-build-2229161-53135/root/chroot_tmpdir/scmroot/ostree
Cloning into '/var/lib/mock/f40-build-2229161-53135/root/chroot_tmpdir/scmroot/ostree'...
$ git fetch origin a677afb01ba2fbde9c0bc6a42d3ca4817adc7bff:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ostree
 * [new ref]         a677afb01ba2fbde9c0bc6a42d3ca4817adc7bff -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a677afb Backport https://github.com/ostreedev/ostree/pull/3130