Subject: Re: color.diff.whitespace unused on removed lines

From: Junio C Hamano <[email-masked]>
Date: Tue, 04 Oct 2016 10:57:11 -0700

Jeff King <[email-masked]> writes:

> On Tue, Oct 04, 2016 at 05:35:23PM +0200, Sandro Santilli wrote:
>
>> > We later did b8767f7 (diff.c: --ws-error-highlight=<kind> option,
>> > 2015-05-26) to let you see them on other lines, though. I think that
>> > would do what you want.
>> 
>> Thanks, it does do what I want.
>> Any chance to specify it in the config file that I want it
>> always to behave in a certain way ?
>
> No, I don't think there's currently a matching config option. You can
> use an alias, or propose a patch to add a config option.

The final shape of such a patch would include something like the
attached.  It would need to be split into a few patches and then get
additional tests and documentation written, so I won't be committing
it myself in this shape.

 diff.c | 84 +++++++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 50 insertions(+), 34 deletions(-)

diff --git a/diff.c b/diff.c
index a178ed39bc..a2193c3aea 100644
--- a/diff.c
+++ b/diff.c
@@ -43,6 +43,7 @@ static int diff_stat_graph_width;
 static int diff_dirstat_permille_default = 30;
 static struct diff_options default_diff_options;
 static long diff_algorithm;
+static unsigned ws_error_highlight_default = WSEH_NEW;
 
 static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_RESET,
@@ -172,6 +173,42 @@ long parse_algorithm_value(const char *value)
 	return -1;
 }
 
+static int parse_one_token(const char **arg, const char *token)
+{
+	const char *rest;
+	if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
+		*arg = rest;
+		return 1;
+	}
+	return 0;
+}
+
+static int parse_ws_error_highlight(const char *arg)
+{
+	const char *orig_arg = arg;
+	unsigned val = 0;
+	while (*arg) {
+		if (parse_one_token(&arg, "none"))
+			val = 0;
+		else if (parse_one_token(&arg, "default"))
+			val = WSEH_NEW;
+		else if (parse_one_token(&arg, "all"))
+			val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
+		else if (parse_one_token(&arg, "new"))
+			val |= WSEH_NEW;
+		else if (parse_one_token(&arg, "old"))
+			val |= WSEH_OLD;
+		else if (parse_one_token(&arg, "context"))
+			val |= WSEH_CONTEXT;
+		else {
+			return (orig_arg - arg);
+		}
+		if (*arg)
+			arg++;
+	}
+	return val;
+}
+
 /*
  * These are to give UI layer defaults.
  * The core-level commands such as git-diff-files should
@@ -254,6 +291,11 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "diff.wserrorhighlight")) {
+		ws_error_highlight_default = parse_ws_error_highlight(value);
+		return 0;
+	}
+
 	if (git_diff_heuristic_config(var, value, cb) < 0)
 		return -1;
 	if (git_color_config(var, value, cb) < 0)
@@ -3307,7 +3349,7 @@ void diff_setup(struct diff_options *options)
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
 	options->context = diff_context_default;
-	options->ws_error_highlight = WSEH_NEW;
+	options->ws_error_highlight = ws_error_highlight_default;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
 	/* pathchange left =NULL by default */
@@ -3698,40 +3740,14 @@ static void enable_patch_output(int *fmt) {
 	*fmt |= DIFF_FORMAT_PATCH;
 }
 
-static int parse_one_token(const char **arg, const char *token)
+static int parse_ws_error_highlight_opt(struct diff_options *opt, const char *arg)
 {
-	const char *rest;
-	if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
-		*arg = rest;
-		return 1;
-	}
-	return 0;
-}
+	int val = parse_ws_error_highlight(arg);
 
-static int parse_ws_error_highlight(struct diff_options *opt, const char *arg)
-{
-	const char *orig_arg = arg;
-	unsigned val = 0;
-	while (*arg) {
-		if (parse_one_token(&arg, "none"))
-			val = 0;
-		else if (parse_one_token(&arg, "default"))
-			val = WSEH_NEW;
-		else if (parse_one_token(&arg, "all"))
-			val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
-		else if (parse_one_token(&arg, "new"))
-			val |= WSEH_NEW;
-		else if (parse_one_token(&arg, "old"))
-			val |= WSEH_OLD;
-		else if (parse_one_token(&arg, "context"))
-			val |= WSEH_CONTEXT;
-		else {
-			error("unknown value after ws-error-highlight=%.*s",
-			      (int)(arg - orig_arg), orig_arg);
-			return 0;
-		}
-		if (*arg)
-			arg++;
+	if (val < 0) {
+		error("unknown value after ws-error-highlight=%.*s",
+		      -val, arg);
+		return 0;
 	}
 	opt->ws_error_highlight = val;
 	return 1;
@@ -3950,7 +3966,7 @@ int diff_opt_parse(struct diff_options *options,
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
 	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
-		return parse_ws_error_highlight(options, arg);
+		return parse_ws_error_highlight_opt(options, arg);
 
 	/* misc options */
 	else if (!strcmp(arg, "-z"))