color: allow colors to be prefixed with "reset"

"reset" was previously treated as a standalone special color name
representing `\e[m`. Now, it can apply to other color properties,
allowing exact specifications without implicit attribute inheritance.

For example, "reset green" now renders `\e[;32m`, which is interpreted
as "reset everything; then set foreground to green". This means the
background and other attributes are also reset to their defaults.

Previously, this was impossible to represent in a single color:
"reset" could be specified alone, or a color with attributes, but some
thing like clearing a background color were impossible.

There is a separate change that introduces the "default" color name to
assist with that, but even then, the above could only to be represented
by explicitly disabling each of the attributes:
  green default no-bold no-dim no-italic no-ul no-blink no-reverse no-strike

Signed-off-by: Robert Estelle <robertestelle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/color.c b/color.c
index a5fa9b79a7..4f884c6b3d 100644
--- a/color.c
+++ b/color.c
@@ -255,6 +255,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
 	const char *ptr = value;
 	int len = value_len;
 	char *end = dst + COLOR_MAXLEN;
+	unsigned int has_reset = 0;
 	unsigned int attr = 0;
 	struct color fg = { COLOR_UNSPECIFIED };
 	struct color bg = { COLOR_UNSPECIFIED };
@@ -269,12 +270,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
 		return 0;
 	}
 
-	if (!strncasecmp(ptr, "reset", len)) {
-		xsnprintf(dst, end - dst, GIT_COLOR_RESET);
-		return 0;
-	}
-
-	/* [fg [bg]] [attr]... */
+	/* [reset] [fg [bg]] [attr]... */
 	while (len > 0) {
 		const char *word = ptr;
 		struct color c = { COLOR_UNSPECIFIED };
@@ -291,6 +287,11 @@ int color_parse_mem(const char *value, int value_len, char *dst)
 			len--;
 		}
 
+		if (match_word(word, wordlen, "reset")) {
+			has_reset = 1;
+			continue;
+		}
+
 		if (!parse_color(&c, word, wordlen)) {
 			if (fg.type == COLOR_UNSPECIFIED) {
 				fg = c;
@@ -316,13 +317,16 @@ int color_parse_mem(const char *value, int value_len, char *dst)
 	*dst++ = (x); \
 } while(0)
 
-	if (attr || !color_empty(&fg) || !color_empty(&bg)) {
+	if (has_reset || attr || !color_empty(&fg) || !color_empty(&bg)) {
 		int sep = 0;
 		int i;
 
 		OUT('\033');
 		OUT('[');
 
+		if (has_reset)
+			sep++;
+
 		for (i = 0; attr; i++) {
 			unsigned bit = (1 << i);
 			if (!(attr & bit))