Pleroma.Upload.Filter.Dedupe: sharding directory structure

Dedupe now uses a three-level sharding directory structure to improve performance when many files are uploaded and stored on a filesystem instead of an object store. (note: Minio still affected as it still uses a traditional filesystem)

This does not help if you already have hundreds of thousands of files uploaded. The media URLs are permanently part of the activity so the files cannot be relocated. A motivated user could write a tool to move the files and perhaps write an Nginx or equivalent redirect to make the files still accessible, but that is beyond the scope of this change.

test/pleroma/object_test.exs

@@ -174,8 +174,9 @@ defmodule Pleroma.ObjectTest do
 
       filename = Path.basename(href)
 
-      assert {:ok, files} = File.ls(uploads_dir)
-      assert filename in files
+      expected_path = Path.join([uploads_dir, Pleroma.Upload.Filter.Dedupe.shard_path(filename)])
+
+      assert File.exists?(expected_path)
 
       Object.delete(note)
 
@@ -183,8 +184,7 @@ defmodule Pleroma.ObjectTest do
 
       assert Object.get_by_id(note.id).data["deleted"]
       assert Object.get_by_id(attachment.id) == nil
-      assert {:ok, files} = File.ls(uploads_dir)
-      refute filename in files
+      refute File.exists?(expected_path)
     end
 
     test "with objects that have legacy data.url attribute" do