color: allow multiple attributes

In configuration files (and "git config --color" command line), we
supported one and only one attribute after foreground and background
color.  Accept combinations of attributes, e.g.

    [diff.color]
            old = red reverse bold

Signed-off-by: Junio C Hamano <gitster@pobox.com>

color.c

@@ -49,7 +49,7 @@ void color_parse_mem(const char *value, int value_len, const char *var,
 {
 	const char *ptr = value;
 	int len = value_len;
-	int attr = -1;
+	unsigned int attr = 0;
 	int fg = -2;
 	int bg = -2;
 
@@ -58,7 +58,7 @@ void color_parse_mem(const char *value, int value_len, const char *var,
 		return;
 	}
 
-	/* [fg [bg]] [attr] */
+	/* [fg [bg]] [attr]... */
 	while (len > 0) {
 		const char *word = ptr;
 		int val, wordlen = 0;
@@ -87,19 +87,27 @@ void color_parse_mem(const char *value, int value_len, const char *var,
 			goto bad;
 		}
 		val = parse_attr(word, wordlen);
-		if (val < 0 || attr != -1)
+		if (0 <= val)
+			attr |= (1 << val);
+		else
 			goto bad;
-		attr = val;
 	}
 
-	if (attr >= 0 || fg >= 0 || bg >= 0) {
+	if (attr || fg >= 0 || bg >= 0) {
 		int sep = 0;
+		int i;
 
 		*dst++ = '\033';
 		*dst++ = '[';
-		if (attr >= 0) {
-			*dst++ = '0' + attr;
-			sep++;
+
+		for (i = 0; attr; i++) {
+			unsigned bit = (1 << i);
+			if (!(attr & bit))
+				continue;
+			attr &= ~bit;
+			if (sep++)
+				*dst++ = ';';
+			*dst++ = '0' + i;
 		}
 		if (fg >= 0) {
 			if (sep++)

color.h

@@ -1,8 +1,20 @@
 #ifndef COLOR_H
 #define COLOR_H
 
-/* "\033[1;38;5;2xx;48;5;2xxm\0" is 23 bytes */
-#define COLOR_MAXLEN 24
+/*  2 + (2 * num_attrs) + 8 + 1 + 8 + 'm' + NUL */
+/* "\033[1;2;4;5;7;38;5;2xx;48;5;2xxm\0" */
+/*
+ * The maximum length of ANSI color sequence we would generate:
+ * - leading ESC '['            2
+ * - attr + ';'                 2 * 8 (e.g. "1;")
+ * - fg color + ';'             9 (e.g. "38;5;2xx;")
+ * - fg color + ';'             9 (e.g. "48;5;2xx;")
+ * - terminating 'm' NUL        2
+ *
+ * The above overcounts attr (we only use 5 not 8) and one semicolon
+ * but it is close enough.
+ */
+#define COLOR_MAXLEN 40
 
 /*
  * This variable stores the value of color.ui

t/t4026-color.sh

@@ -8,14 +8,13 @@ test_description='Test diff/status color escape codes'
 
 color()
 {
-	git config diff.color.new "$1" &&
-	test "`git config --get-color diff.color.new`" = "$2"
+	actual=$(git config --get-color no.such.slot "$1") &&
+	test "$actual" = "$2"
 }
 
 invalid_color()
 {
-	git config diff.color.new "$1" &&
-	test -z "`git config --get-color diff.color.new 2>/dev/null`"
+	test_must_fail git config --get-color no.such.slot "$1"
 }
 
 test_expect_success 'reset' '
@@ -42,6 +41,14 @@ test_expect_success 'fg bg attr' '
 	color "blue red ul" "[4;34;41m"
 '
 
+test_expect_success 'fg bg attr...' '
+	color "blue bold dim ul blink reverse" "[1;2;4;5;7;34m"
+'
+
+test_expect_success 'long color specification' '
+	color "254 255 bold dim ul blink reverse" "[1;2;4;5;7;38;5;254;48;5;255m"
+'
+
 test_expect_success '256 colors' '
 	color "254 bold 255" "[1;38;5;254;48;5;255m"
 '