rev-list: pass diffopt->use_colors through to pretty-print

When rev-list pretty-prints a commit, it creates a new
pretty_print_context and copies items from the rev_info
struct. We don't currently copy the "use_color" field,
though. Nobody seems to have noticed because the only part
of pretty.c that cares is the %C(auto,...) placeholder, and
presumably not many people use that with the rev-list
plumbing (as opposed to with git-log).

It will become more noticeable in a future patch, though,
when we start treating all user-format colors as auto-colors
(in which case it would become impossible to format colors
with rev-list, even with --color=always).

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

builtin/rev-list.c

@@ -122,6 +122,7 @@ static void show_commit(struct commit *commit, void *data)
 		ctx.date_mode_explicit = revs->date_mode_explicit;
 		ctx.fmt = revs->commit_format;
 		ctx.output_encoding = get_log_output_encoding();
+		ctx.color = revs->diffopt.use_color;
 		pretty_print_commit(&ctx, commit, &buf);
 		if (buf.len) {
 			if (revs->commit_format != CMIT_FMT_ONELINE)

t/t6006-rev-list-format.sh

@@ -245,6 +245,17 @@ test_expect_success '%C(auto) respects --no-color' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rev-list %C(auto,...) respects --color' '
+	git rev-list --color --format="%C(auto,green)foo%C(auto,reset)" \
+		-1 HEAD >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	cat >expect <<-EOF &&
+	commit $(git rev-parse HEAD)
+	<GREEN>foo<RESET>
+	EOF
+	test_cmp expect actual
+'
+
 iconv -f utf-8 -t $test_encoding > commit-msg <<EOF
 Test printing of complex bodies