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, 8 insertions, 0 deletions

diff --git a/ref-filter.c b/ref-filter.c
index 129a636..bc591f4 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -104,6 +104,12 @@ static void color_atom_parser(const struct ref_format *format, struct used_atom
 		die(_("expected format: %%(color:<color>)"));
 	if (color_parse(color_value, atom->u.color) < 0)
 		die(_("unrecognized color: %%(color:%s)"), color_value);
+	/*
+	 * We check this after we've parsed the color, which lets us complain
+	 * about syntactically bogus color names even if they won't be used.
+	 */
+	if (!want_color(format->use_color))
+		color_parse("", atom->u.color);
 }
 
 static void refname_atom_parser_internal(struct refname_atom *atom,
@@ -675,6 +681,8 @@ int verify_ref_format(struct ref_format *format)
 		if (skip_prefix(used_atom[at].name, "color:", &color))
 			format->need_color_reset_at_eol = !!strcmp(color, "reset");
 	}
+	if (format->need_color_reset_at_eol && !want_color(format->use_color))
+		format->need_color_reset_at_eol = 0;
 	return 0;
 }