diff.c: emit_diff_symbol learns DIFF_SYMBOL_FILEPAIR_{PLUS, MINUS}

We have to use fprintf instead of emit_line, because we want to emit the
tab after the color. This is important for ancient versions of gnu patch
AFAICT, although we probably do not want to feed colored output to the
patch utility, such that it would not matter if the trailing tab is
colored. Keep the corner case as-is though.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -561,6 +561,8 @@ static void emit_line(struct diff_options *o, const char *set, const char *reset
 }
 
 enum diff_symbol {
+	DIFF_SYMBOL_FILEPAIR_PLUS,
+	DIFF_SYMBOL_FILEPAIR_MINUS,
 	DIFF_SYMBOL_WORDS_PORCELAIN,
 	DIFF_SYMBOL_WORDS,
 	DIFF_SYMBOL_CONTEXT,
@@ -611,7 +613,7 @@ static void emit_diff_symbol(struct diff_options *o, enum diff_symbol s,
 			     const char *line, int len, unsigned flags)
 {
 	static const char *nneof = " No newline at end of file\n";
-	const char *context, *reset, *set;
+	const char *context, *reset, *set, *meta;
 	switch (s) {
 	case DIFF_SYMBOL_NO_LF_EOF:
 		context = diff_get_color_opt(o, DIFF_CONTEXT);
@@ -673,6 +675,20 @@ static void emit_diff_symbol(struct diff_options *o, enum diff_symbol s,
 		}
 		emit_line(o, context, reset, line, len);
 		break;
+	case DIFF_SYMBOL_FILEPAIR_PLUS:
+		meta = diff_get_color_opt(o, DIFF_METAINFO);
+		reset = diff_get_color_opt(o, DIFF_RESET);
+		fprintf(o->file, "%s%s+++ %s%s%s\n", diff_line_prefix(o), meta,
+			line, reset,
+			strchr(line, ' ') ? "\t" : "");
+		break;
+	case DIFF_SYMBOL_FILEPAIR_MINUS:
+		meta = diff_get_color_opt(o, DIFF_METAINFO);
+		reset = diff_get_color_opt(o, DIFF_RESET);
+		fprintf(o->file, "%s%s--- %s%s%s\n", diff_line_prefix(o), meta,
+			line, reset,
+			strchr(line, ' ') ? "\t" : "");
+		break;
 	default:
 		die("BUG: unknown diff symbol");
 	}
@@ -844,8 +860,6 @@ static void emit_rewrite_diff(const char *name_a,
 			      struct diff_options *o)
 {
 	int lc_a, lc_b;
-	const char *name_a_tab, *name_b_tab;
-	const char *metainfo = diff_get_color(o->use_color, DIFF_METAINFO);
 	const char *fraginfo = diff_get_color(o->use_color, DIFF_FRAGINFO);
 	const char *reset = diff_get_color(o->use_color, DIFF_RESET);
 	static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
@@ -865,8 +879,6 @@ static void emit_rewrite_diff(const char *name_a,
 
 	name_a += (*name_a == '/');
 	name_b += (*name_b == '/');
-	name_a_tab = strchr(name_a, ' ') ? "\t" : "";
-	name_b_tab = strchr(name_b, ' ') ? "\t" : "";
 
 	strbuf_reset(&a_name);
 	strbuf_reset(&b_name);
@@ -893,11 +905,13 @@ static void emit_rewrite_diff(const char *name_a,
 
 	lc_a = count_lines(data_one, size_one);
 	lc_b = count_lines(data_two, size_two);
-	fprintf(o->file,
-		"%s%s--- %s%s%s\n%s%s+++ %s%s%s\n%s%s@@ -",
-		line_prefix, metainfo, a_name.buf, name_a_tab, reset,
-		line_prefix, metainfo, b_name.buf, name_b_tab, reset,
-		line_prefix, fraginfo);
+
+	emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_MINUS,
+			 a_name.buf, a_name.len, 0);
+	emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_PLUS,
+			 b_name.buf, b_name.len, 0);
+
+	fprintf(o->file, "%s%s@@ -", line_prefix, fraginfo);
 	if (!o->irreversible_delete)
 		print_line_count(o->file, lc_a);
 	else
@@ -1365,10 +1379,8 @@ static void find_lno(const char *line, struct emit_callback *ecbdata)
 static void fn_out_consume(void *priv, char *line, unsigned long len)
 {
 	struct emit_callback *ecbdata = priv;
-	const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 	struct diff_options *o = ecbdata->opt;
-	const char *line_prefix = diff_line_prefix(o);
 
 	o->found_changes = 1;
 
@@ -1379,15 +1391,12 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 	}
 
 	if (ecbdata->label_path[0]) {
-		const char *name_a_tab, *name_b_tab;
-
-		name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
-		name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";
-
-		fprintf(o->file, "%s%s--- %s%s%s\n",
-			line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);
-		fprintf(o->file, "%s%s+++ %s%s%s\n",
-			line_prefix, meta, ecbdata->label_path[1], reset, name_b_tab);
+		emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_MINUS,
+				 ecbdata->label_path[0],
+				 strlen(ecbdata->label_path[0]), 0);
+		emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_PLUS,
+				 ecbdata->label_path[1],
+				 strlen(ecbdata->label_path[1]), 0);
 		ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
 	}