[PATCH v3 0/5] built-in add -p: support diff-so-fancy better

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

Philippe Blain reported in
https://lore.kernel.org/git/ecf6f5be-22ca-299f-a8f1-bda38e5ca246@gmail.com
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 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 (5):
  t3701: redefine what is "bogus" output of a diff filter
  add -p: gracefully ignore unparseable hunk headers in colored diffs
  add -p: insert space in colored hunk header as needed
  add -p: handle `diff-so-fancy`'s hunk headers better
  add -p: ignore dirty submodules

 add-patch.c                | 49 ++++++++++++++++++++++++++++++--------
 t/t3701-add-interactive.sh | 35 ++++++++++++++++++++++++++-
 2 files changed, 73 insertions(+), 11 deletions(-)


base-commit: 07ee72db0e97b5c233f8ada0abb412248c2f1c6f
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1336%2Fdscho%2Fdiff-so-fancy-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1336/dscho/diff-so-fancy-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1336

Range-diff vs v2:

 1:  74ab50eeb1c = 1:  a01fa5d25e4 t3701: redefine what is "bogus" output of a diff filter
 2:  b07f85a0359 ! 2:  cbe833bd141 add -p: gracefully ignore unparseable hunk headers in colored diffs
     @@ Commit message
      
          [diff-so-fancy]: https://github.com/so-fancy/diff-so-fancy
      
     +    Reported-by: Philippe Blain <levraiphilippeblain@gmail.com>
          Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
      
       ## add-patch.c ##
     @@ t/t3701-add-interactive.sh: test_expect_success 'detect bogus diffFilter output'
       	force_color test_must_fail git add -p <y
       '
       
     -+test_expect_success 'gracefully fail to parse colored hunk header' '
     ++test_expect_success 'handle iffy colored hunk headers' '
      +	git reset --hard &&
      +
      +	echo content >test &&
     -+	test_config interactive.diffFilter "sed s/@@/XX/g" &&
     -+	printf y >y &&
     -+	force_color git add -p <y
     ++	printf n >n &&
     ++	force_color git -c interactive.diffFilter="sed s/@@/XX/g" \
     ++		add -p <n
      +'
      +
     - test_expect_success 'diff.algorithm is passed to `git diff-files`' '
     + test_expect_success 'handle very large filtered diff' '
       	git reset --hard &&
     - 
     + 	# The specific number here is not important, but it must
 3:  9dac9f74d2e ! 3:  7a9f0b107e6 add -p: handle `diff-so-fancy`'s hunk headers better
     @@ Metadata
      Author: Johannes Schindelin <Johannes.Schindelin@gmx.de>
      
       ## Commit message ##
     -    add -p: handle `diff-so-fancy`'s hunk headers better
     +    add -p: insert space in colored hunk header as needed
      
     -    The `diff-so-fancy` diff colorizer produces hunk headers that look
     -    nothing like the built-in `add -p` expects: there is no `@@ ... @@` line
     -    range, and therefore the parser cannot determine where any extra
     -    information starts, such as the function name that is often added to
     -    those hunk header lines.
     +    We are about to teach `git add -p` to show the entire hunk header if the
     +    `@@ ... @@` line range cannot be parsed. Previously, we showed only the
     +    remainder of that hunk header as an "colored_extra" part.
      
     -    However, we can do better than simply swallowing the unparseable hunk
     -    header. In the `diff-so-fancy` case, it shows something like `@ file:1
     -    @`. Let's just show the complete hunk header because it probably offers
     -    useful information.
     +    To prepare for that, detect if that "colored_extra" part starts with any
     +    non-whitespace character (ignoring ANSI escape sequences) and insert a
     +    space, to make the output much more pleasant.
     +
     +    Note that this has an effect already before we make `git add -p` more
     +    lenient when parsing the hunk headers: diff filters could already remove
     +    the space after the line range, which is precisely what we do in the
     +    regression test introduced by this commit.
      
          Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
      
     @@ add-patch.c
       
       enum prompt_mode_type {
       	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_ADDITION, PROMPT_HUNK,
     -@@ add-patch.c: static int parse_hunk_header(struct add_p_state *s, struct hunk *hunk)
     - 		header->colored_extra_start = p + 3 - s->colored.buf;
     - 	else
     - 		/* could not parse colored hunk header, showing nothing */
     --		header->colored_extra_start = hunk->colored_start;
     -+		header->colored_extra_start = line - s->colored.buf;
     - 	header->colored_extra_end = hunk->colored_start;
     +@@ add-patch.c: static size_t find_next_line(struct strbuf *sb, size_t offset)
     + 	return eol - sb->buf + 1;
     + }
       
     - 	return 0;
     ++static int starts_with_non_ws(const char *p, size_t len)
     ++{
     ++	for (;;) {
     ++		size_t skip;
     ++
     ++		if (!len || isspace(*p))
     ++			return 0;
     ++		skip = display_mode_esc_sequence_len(p);
     ++		if (!skip)
     ++			return 1;
     ++		if (skip > len)
     ++			return 0;
     ++		p += skip;
     ++		len -= skip;
     ++	}
     ++}
     ++
     + static void render_hunk(struct add_p_state *s, struct hunk *hunk,
     + 			ssize_t delta, int colored, struct strbuf *out)
     + {
      @@ add-patch.c: static void render_hunk(struct add_p_state *s, struct hunk *hunk,
       		size_t len;
       		unsigned long old_offset = header->old_offset;
     @@ add-patch.c: static void render_hunk(struct add_p_state *s, struct hunk *hunk,
       			p = s->colored.buf + header->colored_extra_start;
       			len = header->colored_extra_end
       				- header->colored_extra_start;
     -+			if (utf8_strnwidth(p, len, 1 /* skip ANSI */) > 0)
     -+				needs_extra_space = 1;
     ++			needs_extra_space = starts_with_non_ws(p, len);
       		}
       
       		if (s->mode->is_reverse)
     @@ add-patch.c: static void render_hunk(struct add_p_state *s, struct hunk *hunk,
       		else if (colored)
      
       ## t/t3701-add-interactive.sh ##
     -@@ t/t3701-add-interactive.sh: test_expect_success 'gracefully fail to parse colored hunk header' '
     +@@ t/t3701-add-interactive.sh: test_expect_success 'handle iffy colored hunk headers' '
       	echo content >test &&
     - 	test_config interactive.diffFilter "sed s/@@/XX/g" &&
     - 	printf y >y &&
     --	force_color git add -p <y
     -+	force_color git add -p >output 2>&1 <y &&
     -+	grep XX output
     + 	printf n >n &&
     + 	force_color git -c interactive.diffFilter="sed s/@@/XX/g" \
     +-		add -p <n
     ++		add -p <n &&
     ++	force_color git -c interactive.diffFilter="sed \"s/\(.*@@\).*/\1FN/\"" \
     ++		add -p >output 2>&1 <n &&
     ++	if test_have_prereq ADD_I_USE_BUILTIN
     ++	then
     ++		grep "@ FN\$" output
     ++	else
     ++		grep "@FN\$" output
     ++	fi
       '
       
     - test_expect_success 'diff.algorithm is passed to `git diff-files`' '
     + test_expect_success 'handle very large filtered diff' '
 -:  ----------- > 4:  e3e3a178f98 add -p: handle `diff-so-fancy`'s hunk headers better
 4:  540ce27c38a = 5:  cfa6914aee0 add -p: ignore dirty submodules

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