built-in add -p: support diff-so-fancy better

Philippe Blain reported in
https://lore.kernel.org/git/[email protected]
that there is a problem when running the built-in version of git add -p with diff-so-fancy [https://github.com/so-fancy/diff-so-fancy] as diff colorizer. The symptom is this:

    error: could not parse colored hunk header '?[36m?[1m?[38;5;13m@ file:1 @?[1m?[0m'

This patch series addresses that and should fix
https://github.com/so-fancy/diff-so-fancy/issues/437

Changes since v4:

* The second patch was further simplified, avoiding to print extra ANSI sequences if the hunk header is shown verbatim.

Changes since v3:

* Instead of deviating from how the Perl version of git add -p did things, we now teach the built-in version to display hunk headers verbatim when no line range could be parsed out (instead of showing the line range anyways). This was a very good idea of Phillip's, dramatically simplifying the patch series.
* Also, this iteration drops the first patch that claims to redefine what we consider bogus, but only hides an off-by-one. In its stead, there is now a patch that fixes said off-by-one.

Changes since v2:

* Added the appropriate "Reported-by" trailer to the commit message.
* Split out the logic to insert a space between the colored line range and the extra information, if needed.
* That logic was now corrected to see whether that space is really needed.
* To verify that the logic does what we need it to do, the added regression test now specifically tests for that (single) extra space that we want to be inserted.
* Reworded a stale comment that claimed that we might suppress the entire colored hunk header (which we no longer do).
* Rebased to the current tip of the main branch to avoid a merge conflict with 716c1f649e3 (pipe_command(): mark stdin descriptor as non-blocking, 2022-08-17).

Changes since v1:

* Added a commit to ignore dirty submodules just like the Perl version does.

Johannes Schindelin (3):
add -p: detect more mismatches between plain vs colored diffs add -p: gracefully handle unparseable hunk headers in colored diffs add -p: ignore dirty submodules

 add-patch.c                | 33 +++++++++++++++++++++++----------
 t/t3701-add-interactive.sh | 27 +++++++++++++++++++++++++--
 2 files changed, 48 insertions(+), 12 deletions(-)

base-commit: 07ee72db0e97b5c233f8ada0abb412248c2f1c6f
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1336%2Fdscho%2Fdiff-so-fancy-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1336/dscho/diff-so-fancy-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/1336

Range-diff vs v4:

 1:  25187c3a3c2 = 1:  25187c3a3c2 add -p: detect more mismatches between plain vs colored diffs
 2:  cd1c5100506 ! 2:  93d0e3b4d2a add -p: gracefully handle unparseable hunk headers in colored diffs
     @@ Commit message
          we should show the hunk headers verbatim. This is what the Perl version
          of the interactive `add` command did, too.
      
     -    This commit is best viewed with `--color-moved --ignore-space-change`.
     -
          [diff-so-fancy]: https://github.com/so-fancy/diff-so-fancy
      
          Reported-by: Philippe Blain <[email protected]>
     @@ add-patch.c: static int parse_hunk_header(struct add_p_state *s, struct hunk *hu
      -	if (!p)
      -		return error(_("could not parse colored hunk header '%.*s'"),
      -			     (int)(eol - line), line);
     -+	if (p && (p = memmem(p + 4, eol - p - 4, " @@", 3)))
     ++	if (p && (p = memmem(p + 4, eol - p - 4, " @@", 3))) {
      +		header->colored_extra_start = p + 3 - s->colored.buf;
     -+	else {
     ++	} else {
      +		/* could not parse colored hunk header, leave as-is */
      +		header->colored_extra_start = hunk->colored_start;
      +		header->suppress_colored_line_range = 1;
     @@ add-patch.c: static int parse_hunk_header(struct add_p_state *s, struct hunk *hu
       
       	return 0;
      @@ add-patch.c: static void render_hunk(struct add_p_state *s, struct hunk *hunk,
     - 				- header->colored_extra_start;
     - 		}
     - 
     --		if (s->mode->is_reverse)
     --			old_offset -= delta;
     --		else
     --			new_offset += delta;
     --
     --		strbuf_addf(out, "@@ -%lu", old_offset);
     --		if (header->old_count != 1)
     --			strbuf_addf(out, ",%lu", header->old_count);
     --		strbuf_addf(out, " +%lu", new_offset);
     --		if (header->new_count != 1)
     --			strbuf_addf(out, ",%lu", header->new_count);
     --		strbuf_addstr(out, " @@");
     -+		if (!colored || !header->suppress_colored_line_range) {
     -+			if (s->mode->is_reverse)
     -+				old_offset -= delta;
     -+			else
     -+				new_offset += delta;
     + 		if (!colored) {
     + 			p = s->plain.buf + header->extra_start;
     + 			len = header->extra_end - header->extra_start;
     ++		} else if (header->suppress_colored_line_range) {
     ++			strbuf_add(out,
     ++				   s->colored.buf + header->colored_extra_start,
     ++				   header->colored_extra_end -
     ++				   header->colored_extra_start);
      +
     -+			strbuf_addf(out, "@@ -%lu", old_offset);
     -+			if (header->old_count != 1)
     -+				strbuf_addf(out, ",%lu", header->old_count);
     -+			strbuf_addf(out, " +%lu", new_offset);
     -+			if (header->new_count != 1)
     -+				strbuf_addf(out, ",%lu", header->new_count);
     -+			strbuf_addstr(out, " @@");
     -+		}
     - 
     - 		if (len)
     - 			strbuf_add(out, p, len);
     ++			strbuf_add(out, s->colored.buf + hunk->colored_start,
     ++				   hunk->colored_end - hunk->colored_start);
     ++			return;
     + 		} else {
     + 			strbuf_addstr(out, s->s.fraginfo_color);
     + 			p = s->colored.buf + header->colored_extra_start;
      
       ## t/t3701-add-interactive.sh ##
      @@ t/t3701-add-interactive.sh: test_expect_success 'detect bogus diffFilter output' '
     @@ t/t3701-add-interactive.sh: test_expect_success 'detect bogus diffFilter output'
      +	printf n >n &&
      +	force_color git -c interactive.diffFilter="sed s/.*@@.*/XX/" \
      +		add -p >output 2>&1 <n &&
     -+	grep "^[^@]*XX[^@]*$" output
     ++	grep "^XX$" output
      +'
      +
       test_expect_success 'handle very large filtered diff' '

3: 116f0cf5cab = 3: 47943b603b1 add -p: ignore dirty submodules

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