format-patch: ignore ui.color

commit c9bfb953 (want_color: automatically fallback to color.ui,
2011-08-17) introduced a regression where format-patch produces colorized
patches when color.ui is set to "always".

In f3aafa4d (Disable color detection during format-patch, 2006-07-09),
git_format_config was taught to intercept diff.color to avoid passing it
down to git_log_config and later, git_diff_ui_config.

Teach git_format_config to intercept color.ui in the same way.
Helped-by: NJeff King <peff@peff.net>
Signed-off-by: NPang Yan Han <pangyanhan@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -608,7 +608,8 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		string_list_append(&extra_cc, value);
 		return 0;
 	}
-	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
+	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff") ||
+	    !strcmp(var, "color.ui")) {
 		return 0;
 	}
 	if (!strcmp(var, "format.numbered")) {

t/t4014-format-patch.sh

@@ -869,4 +869,12 @@ test_expect_success 'empty subject prefix does not have extra space' '
 	test_cmp expect actual
 '
 
+test_expect_success 'format patch ignores color.ui' '
+	test_unconfig color.ui &&
+	git format-patch --stdout -1 >expect &&
+	test_config color.ui always &&
+	git format-patch --stdout -1 >actual &&
+	test_cmp expect actual
+'
+
 test_done