Use color.ui variable in scripts too

Signed-off-by: Matthias Kestenholz <mk@spinlock.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-config.txt

@@ -144,6 +144,8 @@ See also <<FILES>>.
 	"auto".  If `stdout-is-tty` is missing, then checks the standard
 	output of the command itself, and exits with status 0 if color
 	is to be used, or exits with status 1 otherwise.
+	When the color setting for `name` is undefined, the command uses
+	`color.ui` as fallback.
 
 --get-color name default::
 

builtin-config.c

@@ -224,6 +224,10 @@ static int git_get_colorbool_config(const char *var, const char *value)
 		get_diff_color_found =
 			git_config_colorbool(var, value, stdout_is_tty);
 	}
+	if (!strcmp(var, "color.ui")) {
+		git_use_color_default = git_config_colorbool(var, value, stdout_is_tty);
+		return 0;
+	}
 	return 0;
 }
 
@@ -251,7 +255,7 @@ static int get_colorbool(int argc, const char **argv)
 		if (!strcmp(get_color_slot, "color.diff"))
 			get_colorbool_found = get_diff_color_found;
 		if (get_colorbool_found < 0)
-			get_colorbool_found = 0;
+			get_colorbool_found = git_use_color_default;
 	}
 
 	if (argc == 1) {