Re: [PATCH v4 0/5] stash: clean up index-mode test merge

> 
> Changes in v4:
> • Drop merge verbosity changes altogether. I was going to
>    save-and-restore, but when looking at the index-merge test case (more
>    below) closer, I noticed that "git apply --cached" reports conflicts
>    on stderr. That is, "git stash apply --index" would report conflicts,
>    and silencing the merge takes that away. So instead let's leave the
>    configured verbosity alone.
> • Only copy resulting index merge tree OID when successful
> • Fix interaction with t5520 (new patch 4/5)
> • Squash test from 3/5 into 5/5, since it requires actually merging
>    trees. I've elected to keep it a separate test for now (contrary to
>    Phillip's suggestion) since it's written and working. Adapting
>    existing tests requires quite a bit more digging into implicit context
>    assumptions ;)

> Changes in v3:
> 
> • Change conflict label for current index
> • Fix memory leak of merge_result
> • Fix order of trees to make the correct merge (cherry-pick)
>      • New test (3/5) to validate this
> • Fix test in 4/5 to assert more details of expected state
> 
> Changes in v2:
> 
> • Do give branch labels for the incore merge, although they are never
>    seen (and clarify commit message as a result, also keeping the
>    merge-ort asserts). Phillip was right: without those, we do segfault
>    on conflicts.
> • Use the ui merge options to keep the same diff algorithm.
> • Use merge_finalize instead of clear_merge_options, and reuse the
>    options between merge calls if they are already initialized.
> • Add a new 2/4 to simplify merge options initialization.
> • Add a new 3/4 with a test case for conflicted index merges.
> 
> v1: <cover.1789853192.git.ben.knoble@gmail.com>
> v2: <cover.1790168285.git.ben.knoble@gmail.com>
> v3: <cover.1790425008.git.ben.knoble@gmail.com>
> 
> [1/5] builtin/stash: remove unused header
> [2/5] stash: prepare merge options earlier
> [3/5] t3903: test failed "stash apply --index"
> [4/5] t5520: don't expire reflogs where it matters
> [5/5] builtin/stash: merge index in-core
> 
>   builtin/stash.c  | 91 ++++++++++++------------------------------------
>   t/t3903-stash.sh | 42 ++++++++++++++++++++++
>   t/t5520-pull.sh  |  6 ++++
>   t/t7600-merge.sh |  9 +++++
>   4 files changed, 79 insertions(+), 69 deletions(-)
> 
> Diff-intervalle contre v3 :
> 1:  6a165c4df4 = 1:  6a165c4df4 builtin/stash: remove unused header
> 2:  d9a9e18f3a ! 2:  35b64ae321 stash: prepare merge options earlier
>      @@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefi
>        		return error(_("cannot apply a stash in the middle of a merge"));
>        
>       +	init_ui_merge_options(&o, the_repository);
>      ++
>      ++	if (quiet)
>      ++		o.verbosity = 0;
>       +
>        	if (index) {
>        		if (oideq(&info->b_tree, &info->i_tree) ||
>      @@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefi
>        	o.branch1 = label_ours ? label_ours : "Updated upstream";
>        	o.branch2 = label_theirs ? label_theirs : "Stashed changes";
>        	o.ancestor = label_base ? label_base : "Stash base";
>      +@@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefix,
>      + 	if (oideq(&info->b_tree, &c_tree))
>      + 		o.branch1 = "Version stash was based on";
>      +
>      +-	if (quiet)
>      +-		o.verbosity = 0;
>      +-
>      + 	if (o.verbosity >= 3)
>      + 		printf_ln(_("Merging %s with %s"), o.branch1, o.branch2);
>      +
> 4:  d39e16905d ! 3:  7b0b317ce0 t3903: test failed "stash apply --index"
>      @@ Commit message
>       
>        ## t/t3903-stash.sh ##
>       @@ t/t3903-stash.sh: setup_stash() {
>      - 	test_cmp expect file
>      + 	test_cmp expect actual
>        '
>        
>       +test_expect_success 'stash apply --index leaves everything untouched on failure' '
> 3:  8b5ea5e6f4 ! 4:  2ac371d2dc t3903: test stash --index merges
>      @@
>        ## Metadata ##
>      -Author: D. Ben Knoble <ben.knoble@gmail.com>
>      +Author: Thomas Bachem <mail@thomasbachem.com>
>       
>        ## Commit message ##
>      -    t3903: test stash --index merges
>      +    t5520: don't expire reflogs where it matters
>       
>      -    A future commit will refactor index handling for applied stashes, and we
>      -    need to take care to get the order of trees right when merging. Add a
>      -    test that covers this case.
>      +    The "--rebase -f with rebased upstream" test computes its fork point
>      +    from the reflog of refs/remotes/me/copy, and the entry it needs is
>      +    the one that the fetch of the test before it wrote. Like every reflog
>      +    entry the suite writes after test_tick, it is dated 2005, so the
>      +    first "git reflog expire --all" after that fetch removes it. Pull
>      +    then finds no fork point and rebases onto the merge head with the
>      +    merge head as the upstream, and the rewound commits come back as a
>      +    conflict.
>       
>      -    Suggested-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>      +    Since 452b12c2e0 (builtin/maintenance: use "geometric" strategy by
>      +    default, 2026-02-24) auto maintenance runs that expiry once the reflog
>      +    of HEAD holds a hundred entries it would remove, the default of
>      +    maintenance.reflog-expire.auto. Which run crosses the threshold
>      +    depends on the entries and maintenance runs before it, so the script
>      +    passed by chance: a stash topic that no longer runs "git reset" from
>      +    "stash apply --index" and a rebase topic that runs auto maintenance
>      +    at the end of "git rebase" together move the expiry between the two
>      +    tests.
>       
>      - ## t/t3903-stash.sh ##
>      -@@ t/t3903-stash.sh: setup_stash() {
>      - 	test_cmp expect actual
>      - '
>      +    Pin the expiry as ea7d894f44 (t34xx: don't expire reflogs where it
>      +    matters, 2026-02-24) did for the rebase tests. That covers a "git gc"
>      +    as well, which expires reflogs on its own, where turning off the auto
>      +    trigger of the reflog-expire task alone would not.
>      +
>      +    Reported-by: Junio C Hamano <gitster@pobox.com>
>      +    Helped-by: D. Ben Knoble <ben.knoble@gmail.com>
>      +    Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>      +    Assisted-by: Claude Fable 5.1
>      +    Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
>      +
>      + ## t/t5520-pull.sh ##
>      +@@ t/t5520-pull.sh: test_pull_autostash_fail () {
>      + }
>        
>      -+# the later "stash -k" test is not expecting us to muck with file so much, so
>      -+# reset when finished
>      -+test_expect_success 'stash apply --index merges the correct trees' '
>      -+	head=$(git rev-parse HEAD) &&
>      -+	test_when_finished "git reset --hard $head" &&
>      -+	test_write_lines A B C >file &&
>      -+	git commit -m setup file &&
>      -+	test_write_lines A B staged >file &&
>      -+	git add file &&
>      -+	test_write_lines A B unstaged >file &&
>      -+	git stash &&
>      -+	test_write_lines committed B C >file &&
>      -+	git commit -m to-be-merged file &&
>      -+	git stash pop --index &&
>      -+	git show :file >actual &&
>      -+	test_write_lines committed B staged >expect &&
>      -+	test_cmp expect actual &&
>      -+	test_write_lines committed B unstaged >expect &&
>      -+	test_cmp expect file
>      -+'
>      + test_expect_success setup '
>      ++	# Commit dates are hardcoded to 2005, and the reflog entries will have
>      ++	# a matching timestamp. Maintenance may thus immediately expire
>      ++	# reflogs if it was running.
>      ++	git config set gc.reflogExpire never &&
>      ++	git config set gc.reflogExpireUnreachable never &&
>       +
>      - test_expect_success 'stash -k' '
>      - 	echo bar3 >file &&
>      - 	echo bar4 >file2 &&
>      + 	echo file >file &&
>      + 	git add file &&
>      + 	git commit -a -m original
> 5:  fde7fb7988 ! 5:  e21b832a6e builtin/stash: merge index in-core
>      @@ Commit message
>           we don't see the usual branch and ancestor labels, but the merge
>           subroutines insist on their presence, so use something simple.
>       
>      +    We need to take care to get the order of trees right when merging. Add a
>      +    test that covers this case.
>      +
>           We *could* swap just the git-reset(1) subprocess with our internal
>           reset_tree() and refresh_index(), which would fix the bug. We'd much
>           prefer to clean up these vestiges of the shell-based git-stash, though.
>      @@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefi
>       -			ret = apply_cached(&out);
>       -			strbuf_release(&out);
>       -			if (ret)
>      -+			o.verbosity = 0;
>      -+
>       +			head = lookup_tree(o.repo, &c_tree);
>       +			merge = lookup_tree(o.repo, &info->i_tree);
>       +			merge_base = lookup_tree(o.repo, &info->b_tree);
>      @@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefi
>       +			merge_incore_nonrecursive(&o, merge_base, head, merge,
>       +						  &result);
>       +
>      -+			oidcpy(&index_tree, &result.tree->object.oid);
>      -+			merge_finalize(&o, &result);
>      -+
>      -+			if (!result.clean)
>      ++			if (!result.clean) {
>      ++				merge_finalize(&o, &result);
>        				return error(_("conflicts in index. "
>        					       "Try without --index."));
>       -
>      @@ builtin/stash.c: static enum stash_apply_result do_apply_stash(const char *prefi
>       -			reset_head();
>       -			discard_index(the_repository->index);
>       -			repo_read_index(the_repository);
>      ++			} else {
>      ++				oidcpy(&index_tree, &result.tree->object.oid);
>      ++				merge_finalize(&o, &result);
>      ++			}
>        		}
>        	}
>        
>       
>      + ## t/t3903-stash.sh ##
>      +@@ t/t3903-stash.sh: setup_stash() {
>      + 	test_cmp expect-index actual-index
>      + '
>      +
>      ++# the later "stash -k" test is not expecting us to muck with file so much, so
>      ++# reset when finished
>      ++test_expect_success 'stash apply --index merges the correct trees' '
>      ++	head=$(git rev-parse HEAD) &&
>      ++	test_when_finished "git reset --hard $head" &&
>      ++	test_write_lines A B C >file &&
>      ++	git commit -m setup file &&
>      ++	test_write_lines A B staged >file &&
>      ++	git add file &&
>      ++	test_write_lines A B unstaged >file &&
>      ++	git stash &&
>      ++	test_write_lines committed B C >file &&
>      ++	git commit -m to-be-merged file &&
>      ++	git stash pop --index &&
>      ++	git show :file >actual &&
>      ++	test_write_lines committed B staged >expect &&
>      ++	test_cmp expect actual &&
>      ++	test_write_lines committed B unstaged >expect &&
>      ++	test_cmp expect file
>      ++'
>      ++
>      + test_expect_success 'stash -k' '
>      + 	echo bar3 >file &&
>      + 	echo bar4 >file2 &&
>      +
>        ## t/t7600-merge.sh ##
>       @@ t/t7600-merge.sh: verify_no_mergehead () {
>        	test_cmp result.1-5 file
> 
> base-commit: d38352cd43ab9745686d697872408bc3249a153f