"Phillip Wood via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
>
> When "add -p" parses diffs, it looks for context lines starting with a
> single space. But when diff.suppressBlankEmpty is in effect, an empty
> context line will omit the space, giving us a true empty line. This
> confuses the parser, which is unable to split based on such a line.
>
> It's tempting to say that we should just make sure that we generate a
> diff without that option. However, although we do not parse hunks that
> the user has manually edited with parse_diff() we do allow the user
> to split such hunks. As POSIX calls the decision of whether to print the
> space here "implementation-defined" we need to handle edited hunks where
> empty context lines omit the space.
>
> So let's handle both cases: a context line either starts with a space or
> consists of a totally empty line by normalizing the first character to a
> space when we parse them. Normalizing the first character rather than
> changing the code to check for a space or newline will hopefully future
> proof against introducing similar bugs if the code is changed.
>
> Reported-by: Ilya Tumaykin <itumaykin@xxxxxxxxx>
> Helped-by: Jeff King <peff@xxxxxxxx>
> Signed-off-by: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
> ---
Well written. Thanks for a pleasant read.
> @@ -953,7 +960,7 @@ static int split_hunk(struct add_p_state *s, struct file_diff *file_diff,
> context_line_count = 0;
>
> while (splittable_into > 1) {
> - ch = s->plain.buf[current];
> + ch = normalize_marker(s->plain.buf + current);
I wondered if &s->plain.buf[current] is easier to grok, but what's
written already is good enough ;-)
There is another explicit mention of ' ' in merge_hunks(). Unless
we are normalizing the buffer here (which I do not think we do),
wouldn't we have to make sure that the code over there also knows
that an empty line in a patch is an unmodified empty line?
if (plain[overlap_end] != ' ')
return error(_("expected context line "
"#%d in\n%.*s"),
