The 'ort' merge backend has been hardened against corrupt trees by
ensuring it aborts under appropriate error conditions.
* en/ort-harden-against-corrupt-trees:
cache-tree: fix verify_cache() to catch non-adjacent D/F conflicts
merge-ort: abort merge when trees have duplicate entries
merge-ort: free diff pairs queue in clear_or_reinit_internal_opts()
merge-ort: drop unnecessary show_all_errors from collect_merge_info()
merge-ort: propagate callback errors from traverse_trees_wrapper()