git-add: warn when adding an ignored file with an explicit request.

We allow otherwise ignored paths to be added to the index by
spelling its path out on the command line, but we would warn the
user about them when we do so.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-add.c

@@ -37,6 +37,9 @@ static void prune_directory(struct dir_struct *dir, const char **pathspec, int p
 			free(entry);
 			continue;
 		}
+		if (entry->ignored_entry)
+			fprintf(stderr, "warning: '%s' is an ignored path.\n",
+				entry->name);
 		*dst++ = entry;
 	}
 	dir->nr = dst - dir->entries;