Re: [PATCH v2 0/2] builtin add -p: fix hunk splitting

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Ævar

On 11/01/2022 12:07, Ævar Arnfjörð Bjarmason wrote:
> 
> On Tue, Jan 11 2022, Phillip Wood via GitGitGadget wrote:
> 
>> Thanks to Junio and Ævar for their comments on V1. I've updated the commit
>> message and added a helper function as suggested.
> 
> This v2 LGTM as far as the functionality of the end-state is concerned.

Thanks for taking a look

> As a remaining nit the complete_file() helper you introduce in 2/2
> changes 2/4 places that increment "hunk->splittable+into".
> 
> I grabbed this PR and came up with this amendmend to it which adds a 2/3
> step that converts 3/3 of them, followed by adding the 4th user in your
> 2/2 (now patch 3/3):
> https://github.com/git/git/compare/master...avar:phillipwood-avar/wip/add-p-fix-hunk-splitting-v2.1
> 
> It changes nothing as far as the end-state is concerned, but I think it
> makes this easier to read & follow. The actual behavior change becomes a
> one-line addition to add-patch.c, instead of being mixed up with the
> refactoring of adding the new helper.
> 
> If you'd like to pick that up & run with it as a v3 that's fine by me,
> and if not that's also fine :) Just a suggestion.

I'm not sure I want to go with your extra changes. I've left some
comments on them below

> @@ -488,12 +499,12 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  	else if (starts_with(p, "@@ ") ||
>  		 (hunk == &file_diff->head &&
>  		  (skip_prefix(p, "deleted file", &deleted)))) {
> -		if (marker == '-' || marker == '+')
> -			/*
> -			 * Should not happen; previous hunk did not end
> -			 * in a context line? Handle it anyway.
> -			 */
> +			hunk->splittable_into++;
> +		/*
> +		 * Should not increment "splittable_into";
> +		 * previous hunk did not end in a context
> +		 * line? Handle it anyway.
> +		 */
> +		complete_file(marker, &hunk->splittable_into);
>  
>  		ALLOC_GROW_BY(file_diff->hunk, file_diff->hunk_nr, 1,
>  			   file_diff->hunk_alloc);

I deliberately left this alone as I think we should probably make this
BUG() out instead of silently accepting an invalid diff.

> @@ -566,8 +577,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>  			    (int)(eol - (plain->buf + file_diff->head.start)),
>  			    plain->buf + file_diff->head.start);
>  
> -		if ((marker == '-' || marker == '+') && *p == ' ')
> -			hunk->splittable_into++;
> +		if (*p == ' ')
> +			complete_file(marker, &hunk->splittable_into);
>  		if (marker && *p != '\\')
>  			marker = *p;
  
Here you are calling complete_file() which has the following comment

      /*
       * Last hunk ended in non-context line (i.e. it
       * appended lines to the file, so there are no
       * trailing context lines).
       */

for all context lines so the function name and comment would need
updating.

Best Wishes

Phillip

> A range-diff between your v2 here and that linked-to
> phillipwood-avar/wip/add-p-fix-hunk-splitting-v2.1:
> 
> 1:  cc8639fc29d = 1:  34392397f04 t3701: clean up hunk splitting tests
> -:  ----------- > 2:  c082176f8c5 add-file.c: use static helper to check marker == +|-
> 2:  b698989e265 ! 3:  defca0baba4 builtin add -p: fix hunk splitting
>      @@ Commit message
>           Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>       
>        ## add-patch.c ##
>      -@@ add-patch.c: static int is_octal(const char *p, size_t len)
>      - 	return 1;
>      - }
>      -
>      -+static void complete_file(char marker, struct hunk *hunk)
>      -+{
>      -+	if (marker == '-' || marker == '+')
>      -+		/*
>      -+		 * Last hunk ended in non-context line (i.e. it
>      -+		 * appended lines to the file, so there are no
>      -+		 * trailing context lines).
>      -+		 */
>      -+		hunk->splittable_into++;
>      -+}
>      -+
>      - static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>      - {
>      - 	struct strvec args = STRVEC_INIT;
>       @@ add-patch.c: static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>        			eol = pend;
>        
>        		if (starts_with(p, "diff ")) {
>      -+			complete_file(marker, hunk);
>      ++			complete_file(marker, &hunk->splittable_into);
>        			ALLOC_GROW_BY(s->file_diff, s->file_diff_nr, 1,
>        				   file_diff_alloc);
>        			file_diff = s->file_diff + s->file_diff_nr - 1;
>      -@@ add-patch.c: static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
>      - 				file_diff->hunk->colored_end = hunk->colored_end;
>      - 		}
>      - 	}
>      --
>      --	if (marker == '-' || marker == '+')
>      --		/*
>      --		 * Last hunk ended in non-context line (i.e. it appended lines
>      --		 * to the file, so there are no trailing context lines).
>      --		 */
>      --		hunk->splittable_into++;
>      -+	complete_file(marker, hunk);
>      -
>      - 	/* non-colored shorter than colored? */
>      - 	if (colored_p != colored_pend) {
>       
>        ## t/t3701-add-interactive.sh ##
>       @@ t/t3701-add-interactive.sh: test_expect_success 'correct message when there is nothing to do' '