diff mbox series

[1/3] diff: have submodule_format logic avoid additional diff headers

Message ID e4414cf630da284bdb11f5613ca0ce6413c6a443.1661926908.git.gitgitgadget@gmail.com (mailing list archive)
State Superseded
Headers show
Series Output fixes for --remerge-diff | expand

Commit Message

Elijah Newren Aug. 31, 2022, 6:21 a.m. UTC 
From: Elijah Newren <newren@gmail.com>

Commit 95433eeed9 ("diff: add ability to insert additional headers for
paths", 2022-02-02) introduced the possibility of additional headers,
created in create_filepairs_for_header_only_notifications().  These are
represented by inserting additional pairs in diff_queued_diff which
always have a mode of 0 and a null_oid.  When these were added, one
code path was noted to assume that at least one of the diff_filespecs
in the pair were valid, and that codepath was corrected.

The submodule_format handling is another codepath with the same issue;
it would operate on these additional headers and attempt to display them
as submodule changes.  Prevent that by explicitly checking for both
modes being 0.

Reported-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
---
 diff.c                  | 6 ++++--
 t/t4069-remerge-diff.sh | 8 ++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

Comments

Junio C Hamano Aug. 31, 2022, 10:20 p.m. UTC | #1 
"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Elijah Newren <newren@gmail.com>
>
> Commit 95433eeed9 ("diff: add ability to insert additional headers for
> paths", 2022-02-02) introduced the possibility of additional headers,
> created in create_filepairs_for_header_only_notifications().  These are
> represented by inserting additional pairs in diff_queued_diff which
> always have a mode of 0 and a null_oid.  When these were added, one
> code path was noted to assume that at least one of the diff_filespecs
> in the pair were valid, and that codepath was corrected.
>
> The submodule_format handling is another codepath with the same issue;
> it would operate on these additional headers and attempt to display them
> as submodule changes.  Prevent that by explicitly checking for both
> modes being 0.

It may make sense to give a concrete name for the condition these
new codepaths check, which presumably exists in the part that was
touched in 95433eeed9 when "that codepath was corrected".  I think
you want to treat a diffpair with at least one side with non-zero
mode as a "real" thing (as opposed to the phony "additional headers"
hack), so perhaps

	int diff_filepair_is_phoney(struct diff_filespec *one, 
            			    struct diff_filespec *two)
	{
		return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
	}

or something like that.  The use of the FILE_VALID macro here is
very much deliberate, and tries to match the more recent hack after
this hunk that says:

	if (!DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two)) {
		/*
		 * We should only reach this point for pairs from
		 * create_filepairs_for_header_only_notifications().  For
		 * these, we should avoid the "/dev/null" special casing
		 * above, meaning we avoid showing such pairs as either
		 * "new file" or "deleted file" below.
		 */
		lbl[0] = a_one;
		lbl[1] = b_two;
	}

We shouldn't expect readers to understand (one->mode || two->mode)
is about the same hack as the other one.
Elijah Newren Sept. 1, 2022, 3:44 a.m. UTC | #2 
On Wed, Aug 31, 2022 at 3:20 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Elijah Newren <newren@gmail.com>
> >
> > Commit 95433eeed9 ("diff: add ability to insert additional headers for
> > paths", 2022-02-02) introduced the possibility of additional headers,
> > created in create_filepairs_for_header_only_notifications().  These are
> > represented by inserting additional pairs in diff_queued_diff which
> > always have a mode of 0 and a null_oid.  When these were added, one
> > code path was noted to assume that at least one of the diff_filespecs
> > in the pair were valid, and that codepath was corrected.
> >
> > The submodule_format handling is another codepath with the same issue;
> > it would operate on these additional headers and attempt to display them
> > as submodule changes.  Prevent that by explicitly checking for both
> > modes being 0.
>
> It may make sense to give a concrete name for the condition these
> new codepaths check, which presumably exists in the part that was
> touched in 95433eeed9 when "that codepath was corrected".  I think
> you want to treat a diffpair with at least one side with non-zero
> mode as a "real" thing (as opposed to the phony "additional headers"
> hack), so perhaps
>
>         int diff_filepair_is_phoney(struct diff_filespec *one,
>                                     struct diff_filespec *two)
>         {
>                 return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
>         }
>
> or something like that.  The use of the FILE_VALID macro here is
> very much deliberate, and tries to match the more recent hack after
> this hunk that says:
>
>         if (!DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two)) {
>                 /*
>                  * We should only reach this point for pairs from
>                  * create_filepairs_for_header_only_notifications().  For
>                  * these, we should avoid the "/dev/null" special casing
>                  * above, meaning we avoid showing such pairs as either
>                  * "new file" or "deleted file" below.
>                  */
>                 lbl[0] = a_one;
>                 lbl[1] = b_two;
>         }
>
> We shouldn't expect readers to understand (one->mode || two->mode)
> is about the same hack as the other one.

I like that; I'll make that change.
diff mbox series

Patch

diff --git a/diff.c b/diff.c
index 974626a6211..be23f660570 100644
--- a/diff.c
+++ b/diff.c
@@ -3429,14 +3429,16 @@  static void builtin_diff(const char *name_a,
 
 	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
 	    (!one->mode || S_ISGITLINK(one->mode)) &&
-	    (!two->mode || S_ISGITLINK(two->mode))) {
+	    (!two->mode || S_ISGITLINK(two->mode)) &&
+	    (one->mode || two->mode)) {
 		show_submodule_diff_summary(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
 		return;
 	} else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
 		   (!one->mode || S_ISGITLINK(one->mode)) &&
-		   (!two->mode || S_ISGITLINK(two->mode))) {
+		   (!two->mode || S_ISGITLINK(two->mode)) &&
+		   (one->mode || two->mode)) {
 		show_submodule_inline_diff(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
diff --git a/t/t4069-remerge-diff.sh b/t/t4069-remerge-diff.sh
index 9e7cac68b1c..e3e6fbd97b2 100755
--- a/t/t4069-remerge-diff.sh
+++ b/t/t4069-remerge-diff.sh
@@ -185,6 +185,14 @@  test_expect_success 'remerge-diff w/ diff-filter=U: all conflict headers, no dif
 	test_cmp expect actual
 '
 
+test_expect_success 'submodule formatting ignores additional headers' '
+	# Reuses "expect" from last testcase
+
+	git show --oneline --remerge-diff --diff-filter=U --submodule=log >tmp &&
+	sed -e "s/[0-9a-f]\{7,\}/HASH/g" tmp >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'remerge-diff w/ diff-filter=R: relevant file + conflict header' '
 	git log -1 --oneline resolution >tmp &&
 	cat <<-EOF >>tmp &&