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

pathspec.c

@@ -663,7 +663,6 @@ void clear_pathspec(struct pathspec *pathspec)
 			attr_check_free(pathspec->items[i].attr_check);
 	}
 
-	free(pathspec->items);
-	pathspec->items = NULL;
+	FREE_AND_NULL(pathspec->items);
 	pathspec->nr = 0;
 }