__attribute__: mark some functions with LAST_ARG_MUST_BE_NULL

Some varargs functions that use NULL-terminated parameter list were
missing __attributes__ ((sentinel)) aka LAST_ARG_MUST_BE_NULL.

Add them.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

add-patch.c

@@ -300,6 +300,7 @@ static void err(struct add_p_state *s, const char *fmt, ...)
 	va_end(args);
 }
 
+LAST_ARG_MUST_BE_NULL
 static void setup_child_process(struct add_p_state *s,
 				struct child_process *cp, ...)
 {

attr.h

@@ -190,6 +190,8 @@ struct attr_check {
 };
 
 struct attr_check *attr_check_alloc(void);
+
+LAST_ARG_MUST_BE_NULL
 struct attr_check *attr_check_initl(const char *, ...);
 struct attr_check *attr_check_dup(const struct attr_check *check);
 

hook.h

@@ -86,5 +86,6 @@ int run_hooks(const char *hook_name);
  * argument. These things will be used as positional arguments to the
  * hook. This function behaves like the old run_hook_le() API.
  */
+LAST_ARG_MUST_BE_NULL
 int run_hooks_l(const char *hook_name, ...);
 #endif

scalar.c

@@ -70,6 +70,7 @@ static void setup_enlistment_directory(int argc, const char **argv,
 	strbuf_release(&path);
 }
 
+LAST_ARG_MUST_BE_NULL
 static int run_git(const char *arg, ...)
 {
 	struct child_process cmd = CHILD_PROCESS_INIT;