Merge branch 'jc/format-color-auto'

Introduce "log --format=%C(auto,blue)Foo%C(auto,reset)" that does
not color its output when writing to a non-terminal.

* jc/format-color-auto:
  log --format: teach %C(auto,black) to respect color config
  t6006: clean up whitespace

commit.h

@@ -89,6 +89,7 @@ struct pretty_print_context {
 	char *notes_message;
 	struct reflog_walk_info *reflog_info;
 	const char *output_encoding;
+	int color;
 };
 
 struct userformat_want {