Merge branch 'ab/free-and-null'

A common pattern to free a piece of memory and assign NULL to the
pointer that used to point at it has been replaced with a new
FREE_AND_NULL() macro.

* ab/free-and-null:
  *.[ch] refactoring: make use of the FREE_AND_NULL() macro
  coccinelle: make use of the "expression" FREE_AND_NULL() rule
  coccinelle: add a rule to make "expression" code use FREE_AND_NULL()
  coccinelle: make use of the "type" FREE_AND_NULL() rule
  coccinelle: add a rule to make "type" code use FREE_AND_NULL()
  git-compat-util: add a FREE_AND_NULL() wrapper around free(ptr); ptr = NULL

remote-testsvn.c

@@ -66,8 +66,7 @@ static char *read_ref_note(const struct object_id *oid)
 	else if (!msglen || type != OBJ_BLOB) {
 		error("Note contains unusable content. "
 			"Is something else using this notes tree? %s", notes_ref);
-		free(msg);
-		msg = NULL;
+		FREE_AND_NULL(msg);
 	}
 	free_notes(NULL);
 	return msg;