Re: [PATCH 2/4] diff.c: add --output-indicator-{new, old, context}

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Steafn,

On Fri, 10 Aug 2018, Stefan Beller wrote:

> This will prove useful in range-diff in a later patch as we will be able to
> differentiate between adding a new file (that line is starting with +++
> and then the file name) and regular new lines.

Very good!

> It could also be useful for experimentation in new patch formats, i.e.
> we could teach git to emit moved lines with lines other than +/-.
> 
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  diff.c | 21 +++++++++++++++++----
>  diff.h |  5 +++++
>  2 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/diff.c b/diff.c
> index b3cb73eb69a..b75eb085cb3 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -1237,7 +1237,7 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
>  					 struct emitted_diff_symbol *eds)
>  {
>  	static const char *nneof = " No newline at end of file\n";
> -	const char *context, *reset, *set, *set_sign, *meta, *fraginfo;
> +	const char *context, *reset, *set, *set_sign, *meta, *fraginfo, *first;
>  	struct strbuf sb = STRBUF_INIT;
>  
>  	enum diff_symbol s = eds->s;
> @@ -1288,7 +1288,9 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
>  			else if (c == '-')
>  				set = diff_get_color_opt(o, DIFF_FILE_OLD);
>  		}
> -		emit_line_ws_markup(o, set_sign, set, reset, " ", line, len,
> +		first = o->output_indicators[OI_CONTEXT] ?
> +			o->output_indicators[OI_CONTEXT] : " ";
> +		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,

Instead of doing this over and over again, how about

1) setting o->output_indicators to " " in diff_setup()?

2) passing OI_CONTEXT to emit_line_ws_markup() instead of `first`? I.e.
   change it to the index in the output_indicators, with -1 indicating
   "none"?

>  				    flags & (DIFF_SYMBOL_CONTENT_WS_MASK), 0);
>  		break;
>  	case DIFF_SYMBOL_PLUS:
> @@ -1331,7 +1333,10 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
>  				set = diff_get_color_opt(o, DIFF_CONTEXT_BOLD);
>  			flags &= ~DIFF_SYMBOL_CONTENT_WS_MASK;
>  		}
> -		emit_line_ws_markup(o, set_sign, set, reset, "+", line, len,
> +
> +		first = o->output_indicators[OI_NEW] ?
> +			o->output_indicators[OI_NEW] : "+";
> +		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,
>  				    flags & DIFF_SYMBOL_CONTENT_WS_MASK,
>  				    flags & DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF);
>  		break;
> @@ -1374,7 +1379,9 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
>  			else
>  				set = diff_get_color_opt(o, DIFF_CONTEXT_DIM);
>  		}
> -		emit_line_ws_markup(o, set_sign, set, reset, "-", line, len,
> +		first = o->output_indicators[OI_OLD] ?
> +			o->output_indicators[OI_OLD] : "-";
> +		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,
>  				    flags & DIFF_SYMBOL_CONTENT_WS_MASK, 0);
>  		break;
>  	case DIFF_SYMBOL_WORDS_PORCELAIN:
> @@ -4876,6 +4883,12 @@ int diff_opt_parse(struct diff_options *options,
>  		 options->output_format |= DIFF_FORMAT_DIFFSTAT;
>  	} else if (!strcmp(arg, "--no-compact-summary"))
>  		 options->flags.stat_with_summary = 0;
> +	else if (skip_prefix(arg, "--output-indicator-new=", &arg))
> +		options->output_indicators[OI_NEW] = arg;
> +	else if (skip_prefix(arg, "--output-indicator-old=", &arg))
> +		options->output_indicators[OI_OLD] = arg;
> +	else if (skip_prefix(arg, "--output-indicator-context=", &arg))
> +		options->output_indicators[OI_CONTEXT] = arg;
>  
>  	/* renames options */
>  	else if (starts_with(arg, "-B") ||
> diff --git a/diff.h b/diff.h
> index e1e54256c18..2d4097df1c7 100644
> --- a/diff.h
> +++ b/diff.h
> @@ -194,6 +194,11 @@ struct diff_options {
>  	FILE *file;
>  	int close_file;
>  
> +#define OI_NEW 0
> +#define OI_OLD 1
> +#define OI_CONTEXT 2

I could imagine that OI_* is too generic a prefix, and that we would want
to have a prefix that is less prone to collide with other global
constants, such as OUTPUT_INDICATOR_*.

Ciao,
Dscho

> +	const char *output_indicators[3];
> +
>  	struct pathspec pathspec;
>  	pathchange_fn_t pathchange;
>  	change_fn_t change;
> -- 
> 2.18.0.865.gffc8e1a3cd6-goog
> 
>