Re: [PATCH 02/19] diff: move line ending check into emit_hunk_header

From: Junio C Hamano <gitster@pobox.com>
Date: May 15, 2017, 06:48 UTC
Message-ID: <xmqqk25ivcnb.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170514040117.25865-3-sbeller@google.com>

Stefan Beller <sbeller@google.com> writes:

Show 14 quoted lines

> In a later patch, I want to propose an option to detect&color
> moved lines in a diff, which cannot be done in a one-pass over
> the diff. Instead we need to go over the whole diff twice,
> because we cannot detect the first line of the two corresponding
> lines (+ and -) that got moved.
>
> So to prepare the diff machinery for two pass algorithms
> (i.e. buffer it all up and then operate on the result),
> move all emissions to places, such that the only emitting
> function is emit_line_0.
>
> This patch moves code that is conceptually part of
> emit_hunk_header, but was using output in fn_out_consume,
> back to emit_hunk_header.

Makes sort-of sense. If I were selling this patch, I'd remove the first two paragraph and stress on how completing the line inside emit_hunk_header() is conceptually cleaner than doing it outside.

	emit_hunk_header() function is responsible for assembling a
	hunk header and calling emit_line() to send the hunk header
	to the output file.  Its only caller fn_out_consume() needs
	to prepare for a case where the function emits an incomplete
	line and add the terminating LF.

	Instead make sure emit_hunk_header() to always send a
	completed line to emit_line().

or something like that.

Note that I am not saying "buffering the entire diff in-core? why should we support such a use case?". I am saying that this change is a clean-up that is justifiable, without having to answer such a question.

Show 29 quoted lines

>
> Meanwhile simplify it by using a function that is designed for it.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  diff.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/diff.c b/diff.c
> index 3f5bf8b5a4..c2ed605cd0 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -677,6 +677,8 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
>  	}
>  
>  	strbuf_add(&msgbuf, line + len, org_len - len);
> +	strbuf_complete_line(&msgbuf);
> +
>  	emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
>  	strbuf_release(&msgbuf);
>  }
> @@ -1315,8 +1317,6 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
>  		len = sane_truncate_line(ecbdata, line, len);
>  		find_lno(line, ecbdata);
>  		emit_hunk_header(ecbdata, line, len);
> -		if (line[len-1] != '\n')
> -			putc('\n', o->file);
>  		return;
>  	}