builtin: add a repository parameter for builtin functions

In order to reduce the usage of the global the_repository, add a
parameter to builtin functions that will get passed a repository
variable.

This commit uses UNUSED on most of the builtin functions, as subsequent
commits will modify the actual builtins to pass the repository parameter
down.

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/bugreport.c

@@ -98,7 +98,10 @@ static void get_header(struct strbuf *buf, const char *title)
 	strbuf_addf(buf, "\n\n[%s]\n", title);
 }
 
-int cmd_bugreport(int argc, const char **argv, const char *prefix)
+int cmd_bugreport(int argc,
+		  const char **argv,
+		  const char *prefix,
+		  struct repository *repo UNUSED)
 {
 	struct strbuf buffer = STRBUF_INIT;
 	struct strbuf report_path = STRBUF_INIT;