use CALLOC_ARRAY

Add and apply a semantic patch for converting code that open-codes
CALLOC_ARRAY to use it instead.  It shortens the code and infers the
element size automatically.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

patch-ids.c

@@ -124,7 +124,7 @@ struct patch_id *add_commit_patch_id(struct commit *commit,
 	if (!patch_id_defined(commit))
 		return NULL;
 
-	key = xcalloc(1, sizeof(*key));
+	CALLOC_ARRAY(key, 1);
 	if (init_patch_id_entry(key, commit, ids)) {
 		free(key);
 		return NULL;