color: support strike-through attribute

This is the only remaining attribute that is commonly
supported (at least by xterm) that we don't support. Let's
add it for completeness.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -160,8 +160,9 @@ Colors may also be given as numbers between 0 and 255; these use ANSI
 your terminal supports it, you may also specify 24-bit RGB values as
 hex, like `#ff0ab3`.
 +
-The accepted attributes are `bold`, `dim`, `ul`, `blink`, `reverse`, and
-`italic`.  The position of any attributes with respect to the colors
+The accepted attributes are `bold`, `dim`, `ul`, `blink`, `reverse`,
+`italic`, and `strike` (for crossed-out or "strikethrough" letters).
+The position of any attributes with respect to the colors
 (before, after, or in between), doesn't matter. Specific attributes may
 be turned off by prefixing them with `no` or `no-` (e.g., `noreverse`,
 `no-ul`, etc).

color.c

@@ -136,7 +136,8 @@ static int parse_attr(const char *name, size_t len)
 		ATTR("italic",    3, 23),
 		ATTR("ul",        4, 24),
 		ATTR("blink",     5, 25),
-		ATTR("reverse",   7, 27)
+		ATTR("reverse",   7, 27),
+		ATTR("strike",    9, 29)
 #undef ATTR
 	};
 	int negate = 0;

color.h

@@ -17,9 +17,9 @@ struct strbuf;
  * The space for attributes is also slightly overallocated, as
  * the negation for some attributes is the same (e.g., nobold and nodim).
  *
- * We allocate space for 6 attributes.
+ * We allocate space for 7 attributes.
  */
-#define COLOR_MAXLEN 70
+#define COLOR_MAXLEN 75
 
 /*
  * IMPORTANT: Due to the way these color codes are emulated on Windows,

t/t4026-color.sh

@@ -61,8 +61,8 @@ test_expect_success 'long color specification' '
 test_expect_success 'absurdly long color specification' '
 	color \
 	  "#ffffff #ffffff bold nobold dim nodim italic noitalic
-	   ul noul blink noblink reverse noreverse" \
-	  "[1;2;3;4;5;7;22;23;24;25;27;38;2;255;255;255;48;2;255;255;255m"
+	   ul noul blink noblink reverse noreverse strike nostrike" \
+	  "[1;2;3;4;5;7;9;22;23;24;25;27;29;38;2;255;255;255;48;2;255;255;255m"
 '
 
 test_expect_success '0-7 are aliases for basic ANSI color names' '