Re: [PATCH v4 0/7] cherry-pick: add `--empty` for more robust redundant commit handling

[phillip.wood123@gmail.com]

Hi Brian

On 20/03/2024 23:36, Brian Lyles wrote:
> This re-roll contains only minor changes from v3.

Here is the range diff with a couple of comments

1:  5a503a7026 = 1:  5aa3f7cec2 docs: address inaccurate `--empty` default with `--exec`
2:  36278e0d40 = 2:  abb7d7233a docs: clean up `--empty` formatting in git-rebase(1) and git-am(1)
3:  a2f603da50 = 3:  ef8224d286 rebase: update `--empty=ask` to `--empty=stop`
4:  0701f9f9fc ! 4:  21ed2dfb65 sequencer: treat error reading HEAD as unborn branch
     @@ Metadata
      Author: Brian Lyles <brianmlyles@gmail.com>
      
       ## Commit message ##
     -    sequencer: treat error reading HEAD as unborn branch
     +    sequencer: handle unborn branch with `--allow-empty`
      
          When using git-cherry-pick(1) with `--allow-empty` while on an unborn
          branch, an error is thrown. This is inconsistent with the same
          cherry-pick when `--allow-empty` is not specified.
      
     -    Treat a failure reading HEAD as an unborn branch in
     -    `is_index_unchanged`. This is consistent with other sequencer logic such
     -    as `do_pick_commit`. When on an unborn branch, use the `empty_tree` as
     -    the tree to compare against.
     +    Detect unborn branches in `is_index_unchanged`. When on an unborn
     +    branch, use the `empty_tree` as the tree to compare against.
      
          Add a new test to cover this scenario. While modelled off of the
          existing 'cherry-pick on unborn branch' test, some improvements can be
     @@ Commit message
          - Use `git switch --orphan unborn` instead of `git checkout --orphan
            unborn` to avoid the need for a separate `rm -rf *` call
          - Avoid using `--quiet` in the `git diff` call to make debugging easier
     -      in the event of a failure
     +      in the event of a failure. Use simply `--exit-code` instead.
      
          Make these improvements to the existing test as well as the new test.
      
          Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
     +    Helped-by: Junio C Hamano <gitster@pobox.com>
          Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
      
       ## sequencer.c ##
     @@ sequencer.c: static struct object_id *get_cache_tree_oid(struct index_state *ist
      +	const struct object_id *head_tree_oid;
       	struct commit *head_commit;
       	struct index_state *istate = r->index;
     -
     +-
      -	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
      -		return error(_("could not resolve HEAD commit"));
      -
     @@ sequencer.c: static struct object_id *get_cache_tree_oid(struct index_state *ist
      -	 */
      -	if (repo_parse_commit(r, head_commit))
      -		return -1;
     ++	const char *head_name;
     ++
      +	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL)) {
      +		/*
     -+		 * Treat an error reading HEAD as an unborn branch.
     ++		 * Check to see if this is an unborn branch
      +		 */

You are only editing an existing comment here and it is not worth a
re-roll on its own, but for one line comments we prefer

	/* Check to see if this is an unborn branch */

     ++		head_name = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE, &head_oid, NULL);
     ++		if (!head_name || !starts_with(head_name, "refs/heads/") || !is_null_oid(&head_oid))

While we don't mind the occasional line that is a little over 80
characters these really are rather long.

     ++			return error(_("could not resolve HEAD commit"));
      +		head_tree_oid = the_hash_algo->empty_tree;
      +	} else {
      +		head_commit = lookup_commit(r, &head_oid);
     @@ t/t3501-revert-cherry-pick.sh: test_expect_success 'revert forbidden on dirty wo
      -	rm -rf * &&
       	git cherry-pick initial &&
      -	git diff --quiet initial &&
     -+	git diff initial &&
     ++	git diff --exit-code initial &&
      +	test_cmp_rev ! initial HEAD
      +'
      +
     @@ t/t3501-revert-cherry-pick.sh: test_expect_success 'revert forbidden on dirty wo
      +	git branch -D unborn &&
      +	git switch --orphan unborn &&
      +	git cherry-pick initial --allow-empty &&
     -+	git diff initial &&
     ++	git diff --exit-code initial &&
       	test_cmp_rev ! initial HEAD
       '

Thanks for updating these tests
       
5:  3634da0f70 = 5:  5c16a01056 sequencer: do not require `allow_empty` for redundant commit options
6:  e98b414697 = 6:  3ee057e485 cherry-pick: enforce `--keep-redundant-commits` incompatibility
7:  cc4030d8ec ! 7:  0cd4620ef7 cherry-pick: add `--empty` for more robust redundant commit handling
     @@ Documentation/git-cherry-pick.txt: effect to your index in a row.
      +	you to examine the commit. This is the default behavior.
      +--
      ++
     -+Note that this option specifies how to handle a commit that was not initially
     -+empty, but rather became empty due to a previous commit. Commits that were
     -+initially empty will cause the cherry-pick to fail. To force the inclusion of
     -+those commits, use `--allow-empty`.
     ++Note that `--empty=drop` and `--empty=stop` only specify how to handle a
     ++commit that was not initially empty, but rather became empty due to a previous
     ++commit. Commits that were initially empty will still cause the cherry-pick to
     ++fail unless one of `--empty=keep` or `--allow-empty` are specified.
      ++
      +
       --keep-redundant-commits::

The new wording here looks good

Apart from the minor style issues this all looks good to me, thanks
for working on it, it will be a useful addition to be able to drop
cherry-picks that become empty.

Best Wishes

Phillip