ref-filter: consult want_color() before emitting colors

When color placeholders like %(color:red) are used in a
ref-filter format, we unconditionally output the colors,
even if the user has asked us for no colors. This usually
isn't a problem when the user is constructing a --format on
the command line, but it means we may do the wrong thing
when the format is fed from a script or alias. For example:

   $ git config alias.b 'branch --format=%(color:green)%(refname)'
   $ git b --no-color

should probably omit the green color. Likewise, running:

   $ git b >branches

should probably also omit the color, just as we would for
all baked-in coloring (and as we recently started to do for
user-specified colors in --pretty formats).

This commit makes both of those cases work by teaching
the ref-filter code to consult want_color() before
outputting any color. The color flag in ref_format defaults
to "-1", which means we'll consult color.ui, which in turn
defaults to the usual isatty() check on stdout. However,
callers like git-branch which support their own color config
(and command-line options) can override that.

The new tests independently cover all three of the callers
of ref-filter (for-each-ref, tag, and branch). Even though
these seem redundant, it confirms that we've correctly
plumbed through all of the necessary config to make colors
work by default.

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

1 files changed, 31 insertions, 0 deletions

diff --git a/t/t3203-branch-output.sh b/t/t3203-branch-output.sh
index a428ae6703..d2aec0f38b 100755
--- a/t/t3203-branch-output.sh
+++ b/t/t3203-branch-output.sh
@@ -2,6 +2,7 @@
 
 test_description='git branch display tests'
 . ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-terminal.sh
 
 test_expect_success 'make commits' '
 	echo content >file &&
@@ -239,4 +240,34 @@ test_expect_success 'git branch --format option' '
 	test_i18ncmp expect actual
 '
 
+test_expect_success "set up color tests" '
+	echo "<RED>master<RESET>" >expect.color &&
+	echo "master" >expect.bare &&
+	color_args="--format=%(color:red)%(refname:short) --list master"
+'
+
+test_expect_success '%(color) omitted without tty' '
+	TERM=vt100 git branch $color_args >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	test_cmp expect.bare actual
+'
+
+test_expect_success TTY '%(color) present with tty' '
+	test_terminal env TERM=vt100 git branch $color_args >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	test_cmp expect.color actual
+'
+
+test_expect_success 'color.branch=always overrides auto-color' '
+	git -c color.branch=always branch $color_args >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	test_cmp expect.color actual
+'
+
+test_expect_success '--color overrides auto-color' '
+	git branch --color $color_args >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	test_cmp expect.color actual
+'
+
 test_done