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

> 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
>