provide --color option for all ref-filter users

When ref-filter learned about want_color() in 11b087adfd
(ref-filter: consult want_color() before emitting colors,
2017-07-13), it became useful to be able to turn colors off
and on for specific commands. For git-branch, you can do so
with --color/--no-color.

But for git-for-each-ref and git-tag, the other users of
ref-filter, you have no option except to tweak the
"color.ui" config setting. Let's give both of these commands
the usual color command-line options.

This is a bit more obvious as a method for overriding the
config. And it also prepares us for the behavior of "always"
changing (so that we are still left with a way of forcing
color when our output goes to a non-terminal).

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

Documentation/git-for-each-ref.txt

@@ -55,6 +55,11 @@ OPTIONS
 	literally, in the latter case matching completely or from the
 	beginning up to a slash.
 
+--color[=<when>]:
+	Respect any colors specified in the `--format` option. The
+	`<when>` field must be one of `always`, `never`, or `auto` (if
+	`<when>` is absent, behave as if `always` was given).
+
 --shell::
 --perl::
 --python::

Documentation/git-tag.txt

@@ -115,6 +115,11 @@ options for details.
 	variable if it exists, or lexicographic order otherwise. See
 	linkgit:git-config[1].
 
+--color[=<when>]:
+	Respect any colors specified in the `--format` option. The
+	`<when>` field must be one of `always`, `never`, or `auto` (if
+	`<when>` is absent, behave as if `always` was given).
+
 -i::
 --ignore-case::
 	Sorting and filtering tags are case insensitive.

builtin/for-each-ref.c

@@ -36,6 +36,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		OPT_GROUP(""),
 		OPT_INTEGER( 0 , "count", &maxcount, N_("show only <n> matched refs")),
 		OPT_STRING(  0 , "format", &format.format, N_("format"), N_("format to use for the output")),
+		OPT__COLOR(&format.use_color, N_("respect format colors")),
 		OPT_CALLBACK(0 , "sort", sorting_tail, N_("key"),
 			    N_("field name to sort on"), &parse_opt_ref_sorting),
 		OPT_CALLBACK(0, "points-at", &filter.points_at,

builtin/tag.c

@@ -411,6 +411,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		},
 		OPT_STRING(  0 , "format", &format.format, N_("format"),
 			   N_("format to use for the output")),
+		OPT__COLOR(&format.use_color, N_("respect format colors")),
 		OPT_BOOL('i', "ignore-case", &icase, N_("sorting and filtering are case insensitive")),
 		OPT_END()
 	};

t/t6300-for-each-ref.sh

@@ -435,8 +435,8 @@ test_expect_success '%(color) does not show color without tty' '
 	test_cmp expected.bare actual
 '
 
-test_expect_success 'color.ui=always can override tty check' '
+test_expect_success '--color can override tty check' '
-	git -c color.ui=always for-each-ref --format="$color_format" >actual.raw &&
+	git for-each-ref --color --format="$color_format" >actual.raw &&
 	test_decode_color <actual.raw >actual &&
 	test_cmp expected.color actual
 '

t/t7004-tag.sh

@@ -1919,8 +1919,8 @@ test_expect_success TTY '%(color) present with tty' '
 	test_cmp expect.color actual
 '
 
-test_expect_success 'color.ui=always overrides auto-color' '
+test_expect_success '--color overrides auto-color' '
-	git -c color.ui=always tag $color_args >actual.raw &&
+	git tag --color $color_args >actual.raw &&
 	test_decode_color <actual.raw >actual &&
 	test_cmp expect.color actual
 '