revisions API: add a TODO for diff_free(&revs->diffopt)

Add a TODO comment indicating that we should release "diffopt" in
release_revisions(). In a preceding commit we started releasing the
"pruning" member of the same type, but handling "diffopt" will require
us to untangle the "no_free" conditions I added in e900d494dc (diff:
add an API for deferred freeing, 2021-02-11).

Let's leave a TODO comment to that effect, and so that we don't forget
refactor code that was changed to use release_revisions() in earlier
commits to stop using the "diffopt" member after a call to
release_revisions(). This works currently, but would become a logic
error as soon as we started freeing "diffopt". Doing that change now
doesn't harm anything, and future-proofs us against a later change to
release_revisions().

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-lib.c

@@ -651,6 +651,7 @@ int index_differs_from(struct repository *r,
 {
 	struct rev_info rev;
 	struct setup_revision_opt opt;
+	unsigned has_changes;
 
 	repo_init_revisions(r, &rev, NULL);
 	memset(&opt, 0, sizeof(opt));
@@ -662,8 +663,9 @@ int index_differs_from(struct repository *r,
 		diff_flags_or(&rev.diffopt.flags, flags);
 	rev.diffopt.ita_invisible_in_index = ita_invisible_in_index;
 	run_diff_index(&rev, 1);
+	has_changes = rev.diffopt.flags.has_changes;
 	release_revisions(&rev);
-	return (rev.diffopt.flags.has_changes != 0);
+	return (has_changes != 0);
 }
 
 static struct strbuf *idiff_prefix_cb(struct diff_options *opt, void *data)

revision.c

@@ -2956,6 +2956,7 @@ void release_revisions(struct rev_info *revs)
 	date_mode_release(&revs->date_mode);
 	release_revisions_mailmap(revs->mailmap);
 	free_grep_patterns(&revs->grep_filter);
+	/* TODO (need to handle "no_free"): diff_free(&revs->diffopt) */
 	diff_free(&revs->pruning);
 	reflog_walk_info_release(revs->reflog_info);
 	release_revisions_topo_walk_info(revs->topo_walk_info);

wt-status.c

@@ -2545,8 +2545,9 @@ int has_unstaged_changes(struct repository *r, int ignore_submodules)
 	rev_info.diffopt.flags.quick = 1;
 	diff_setup_done(&rev_info.diffopt);
 	result = run_diff_files(&rev_info, 0);
+	result = diff_result_code(&rev_info.diffopt, result);
 	release_revisions(&rev_info);
-	return diff_result_code(&rev_info.diffopt, result);
+	return result;
 }
 
 /**
@@ -2578,8 +2579,9 @@ int has_uncommitted_changes(struct repository *r,
 
 	diff_setup_done(&rev_info.diffopt);
 	result = run_diff_index(&rev_info, 1);
+	result = diff_result_code(&rev_info.diffopt, result);
 	release_revisions(&rev_info);
-	return diff_result_code(&rev_info.diffopt, result);
+	return result;
 }
 
 /**