name-rev: use sizeof(*ptr) instead of sizeof(type) in allocation

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/name-rev.c

@@ -102,7 +102,7 @@ static void name_rev(struct commit *commit,
 	}
 
 	if (name == NULL) {
-		name = xmalloc(sizeof(rev_name));
+		name = xmalloc(sizeof(*name));
 		set_commit_rev_name(commit, name);
 		goto copy_data;
 	} else if (is_better_name(name, taggerdate, distance, from_tag)) {