$ git clone -n https://src.fedoraproject.org/rpms/bird.git /var/lib/mock/f42-build-side-1-3499420-45964/root/chroot_tmpdir/scmroot/bird
Cloning into '/var/lib/mock/f42-build-side-1-3499420-45964/root/chroot_tmpdir/scmroot/bird'...
$ git fetch origin accd78b2f63df4a56fe9312ea4112ca55fb08375:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/bird
 * [new ref]         accd78b2f63df4a56fe9312ea4112ca55fb08375 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at accd78b Upgrade to 2.16.2