Merge branch 'et/pretty-format-c-auto' into maint

The commands in `git log` family take %C(auto) in a custom format
string.  This unconditionally turned the color on, ignoring
--no-color or with --color=auto when the output is not connected to
a tty; this was corrected to make the format truly behave as
"auto".

* et/pretty-format-c-auto:
  format_commit_message: honor `color=auto` for `%C(auto)`

pretty.c

@@ -1063,7 +1063,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	switch (placeholder[0]) {
 	case 'C':
 		if (starts_with(placeholder + 1, "(auto)")) {
-			c->auto_color = 1;
+			c->auto_color = want_color(c->pretty_ctx->color);
 			return 7; /* consumed 7 bytes, "C(auto)" */
 		} else {
 			int ret = parse_color(sb, placeholder, c);

t/t6006-rev-list-format.sh

@@ -184,38 +184,38 @@ commit $head1
 foo
 EOF
 
-test_expect_success '%C(auto) does not enable color by default' '
+test_expect_success '%C(auto,...) does not enable color by default' '
 	git log --format=$AUTO_COLOR -1 >actual &&
 	has_no_color actual
 '
 
-test_expect_success '%C(auto) enables colors for color.diff' '
+test_expect_success '%C(auto,...) enables colors for color.diff' '
 	git -c color.diff=always log --format=$AUTO_COLOR -1 >actual &&
 	has_color actual
 '
 
-test_expect_success '%C(auto) enables colors for color.ui' '
+test_expect_success '%C(auto,...) enables colors for color.ui' '
 	git -c color.ui=always log --format=$AUTO_COLOR -1 >actual &&
 	has_color actual
 '
 
-test_expect_success '%C(auto) respects --color' '
+test_expect_success '%C(auto,...) respects --color' '
 	git log --format=$AUTO_COLOR -1 --color >actual &&
 	has_color actual
 '
 
-test_expect_success '%C(auto) respects --no-color' '
+test_expect_success '%C(auto,...) respects --no-color' '
 	git -c color.ui=always log --format=$AUTO_COLOR -1 --no-color >actual &&
 	has_no_color actual
 '
 
-test_expect_success TTY '%C(auto) respects --color=auto (stdout is tty)' '
+test_expect_success TTY '%C(auto,...) respects --color=auto (stdout is tty)' '
 	test_terminal env TERM=vt100 \
 		git log --format=$AUTO_COLOR -1 --color=auto >actual &&
 	has_color actual
 '
 
-test_expect_success '%C(auto) respects --color=auto (stdout not tty)' '
+test_expect_success '%C(auto,...) respects --color=auto (stdout not tty)' '
 	(
 		TERM=vt100 && export TERM &&
 		git log --format=$AUTO_COLOR -1 --color=auto >actual &&
@@ -223,6 +223,18 @@ test_expect_success '%C(auto) respects --color=auto (stdout not tty)' '
 	)
 '
 
+test_expect_success '%C(auto) respects --color' '
+	git log --color --format="%C(auto)%H" -1 >actual &&
+	printf "\\033[33m%s\\033[m\\n" $(git rev-parse HEAD) >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%C(auto) respects --no-color' '
+	git log --no-color --format="%C(auto)%H" -1 >actual &&
+	git rev-parse HEAD >expect &&
+	test_cmp expect actual
+'
+
 iconv -f utf-8 -t $test_encoding > commit-msg <<EOF
 Test printing of complex bodies