$ git clone -n https://src.fedoraproject.org/rpms/gnome-builder.git /var/lib/mock/f39-build-1984325-43348/root/chroot_tmpdir/scmroot/gnome-builder
Cloning into '/var/lib/mock/f39-build-1984325-43348/root/chroot_tmpdir/scmroot/gnome-builder'...
$ git fetch origin 8fa0eb217f44751e701cde7665ffd2d7edba3f05:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-builder
 * [new ref]         8fa0eb217f44751e701cde7665ffd2d7edba3f05 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8fa0eb2 Update to 45.0