Give the hunk comment its own color

Inspired by the coloring of quilt.

Introduce a separate color and paint the hunk comment part, i.e. the name
of the function, in a separate color "diff.func" (defaults to plain).

Whitespace between hunk header and hunk comment is printed in plain color.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -635,10 +635,10 @@ color.diff.<slot>::
 	Use customized color for diff colorization.  `<slot>` specifies
 	which part of the patch to use the specified color, and is one
 	of `plain` (context text), `meta` (metainformation), `frag`
-	(hunk header), `old` (removed lines), `new` (added lines),
-	`commit` (commit headers), or `whitespace` (highlighting
-	whitespace errors). The values of these variables may be specified as
-	in color.branch.<slot>.
+	(hunk header), 'func' (function in hunk header), `old` (removed lines),
+	`new` (added lines), `commit` (commit headers), or `whitespace`
+	(highlighting whitespace errors). The values of these variables may be
+	specified as in color.branch.<slot>.
 
 color.grep::
 	When set to `always`, always highlight matches.  When `false` (or

combine-diff.c

@@ -524,6 +524,7 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
 	int i;
 	unsigned long lno = 0;
 	const char *c_frag = diff_get_color(use_color, DIFF_FRAGINFO);
+	const char *c_func = diff_get_color(use_color, DIFF_FUNCINFO);
 	const char *c_new = diff_get_color(use_color, DIFF_FILE_NEW);
 	const char *c_old = diff_get_color(use_color, DIFF_FILE_OLD);
 	const char *c_plain = diff_get_color(use_color, DIFF_PLAIN);
@@ -588,7 +589,9 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
 				    comment_end = i;
 			}
 			if (comment_end)
-				putchar(' ');
+				printf("%s%s %s%s", c_reset,
+						    c_plain, c_reset,
+						    c_func);
 			for (i = 0; i < comment_end; i++)
 				putchar(hunk_comment[i]);
 		}

diff.c

@@ -39,6 +39,7 @@ static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_GREEN,	/* NEW */
 	GIT_COLOR_YELLOW,	/* COMMIT */
 	GIT_COLOR_BG_RED,	/* WHITESPACE */
+	GIT_COLOR_NORMAL,	/* FUNCINFO */
 };
 
 static void diff_filespec_load_driver(struct diff_filespec *one);
@@ -60,6 +61,8 @@ static int parse_diff_color_slot(const char *var, int ofs)
 		return DIFF_COMMIT;
 	if (!strcasecmp(var+ofs, "whitespace"))
 		return DIFF_WHITESPACE;
+	if (!strcasecmp(var+ofs, "func"))
+		return DIFF_FUNCINFO;
 	die("bad config variable '%s'", var);
 }
 
@@ -345,6 +348,42 @@ static void emit_add_line(const char *reset,
 	}
 }
 
+static void emit_hunk_header(struct emit_callback *ecbdata,
+			     const char *line, int len)
+{
+	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
+	const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
+	const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
+	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
+	static const char atat[2] = { '@', '@' };
+	const char *cp, *ep;
+
+	/*
+	 * As a hunk header must begin with "@@ -<old>, +<new> @@",
+	 * it always is at least 10 bytes long.
+	 */
+	if (len < 10 ||
+	    memcmp(line, atat, 2) ||
+	    !(ep = memmem(line + 2, len - 2, atat, 2))) {
+		emit_line(ecbdata->file, plain, reset, line, len);
+		return;
+	}
+	ep += 2; /* skip over @@ */
+
+	/* The hunk header in fraginfo color */
+	emit_line(ecbdata->file, frag, reset, line, ep - line);
+
+	/* blank before the func header */
+	for (cp = ep; ep - line < len; ep++)
+		if (*ep != ' ' && *ep != '\t')
+			break;
+	if (ep != cp)
+		emit_line(ecbdata->file, plain, reset, cp, ep - cp);
+
+	if (ep < line + len)
+		emit_line(ecbdata->file, func, reset, ep, line + len - ep);
+}
+
 static struct diff_tempfile *claim_diff_tempfile(void) {
 	int i;
 	for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
@@ -782,9 +821,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 			diff_words_flush(ecbdata);
 		len = sane_truncate_line(ecbdata, line, len);
 		find_lno(line, ecbdata);
-		emit_line(ecbdata->file,
-			  diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO),
-			  reset, line, len);
+		emit_hunk_header(ecbdata, line, len);
 		if (line[len-1] != '\n')
 			putc('\n', ecbdata->file);
 		return;

diff.h

@@ -130,6 +130,7 @@ enum color_diff {
 	DIFF_FILE_NEW = 5,
 	DIFF_COMMIT = 6,
 	DIFF_WHITESPACE = 7,
+	DIFF_FUNCINFO = 8,
 };
 const char *diff_get_color(int diff_use_color, enum color_diff ix);
 #define diff_get_color_opt(o, ix) \

t/t4034-diff-words.sh

@@ -8,6 +8,7 @@ test_expect_success setup '
 
 	git config diff.color.old red
 	git config diff.color.new green
+	git config diff.color.func magenta
 
 '
 
@@ -16,6 +17,7 @@ decrypt_color () {
 		-e 's/.\[1m/<WHITE>/g' \
 		-e 's/.\[31m/<RED>/g' \
 		-e 's/.\[32m/<GREEN>/g' \
+		-e 's/.\[35m/<MAGENTA>/g' \
 		-e 's/.\[36m/<BROWN>/g' \
 		-e 's/.\[m/<RESET>/g'
 }
@@ -70,7 +72,7 @@ cat > expect <<\EOF
 <WHITE>+++ b/post<RESET>
 <BROWN>@@ -1 +1 @@<RESET>
 <RED>h(4)<RESET><GREEN>h(4),hh[44]<RESET>
-<BROWN>@@ -3,0 +4,4 @@ a = b + c<RESET>
+<BROWN>@@ -3,0 +4,4 @@<RESET> <RESET><MAGENTA>a = b + c<RESET>
 
 <GREEN>aa = a<RESET>