use fileuploader dynamic path method in uploads manager and add spec

app/uploaders/file_uploader.rb

@@ -15,7 +15,7 @@ class FileUploader < GitlabUploader
   prepend ObjectStorage::Extension::RecordsUploads
 
   MARKDOWN_PATTERN = %r{\!?\[.*?\]\(/uploads/(?<secret>[0-9a-f]{32})/(?<file>.*?)\)}
-  DYNAMIC_PATH_PATTERN = %r{(?<secret>\h{32})/(?<identifier>.*)}
+  DYNAMIC_PATH_PATTERN = %r{.*(?<secret>\h{32})/(?<identifier>.*)}
 
   after :remove, :prune_store_dir
 
@@ -67,6 +67,10 @@ def self.generate_secret
     SecureRandom.hex
   end
 
+  def self.extract_dynamic_path(path)
+    DYNAMIC_PATH_PATTERN.match(path)
+  end
+
   def upload_paths(identifier)
     [
       File.join(secret, identifier),
@@ -143,7 +147,7 @@ def upload=(value)
     return if apply_context!(value.uploader_context)
 
     # fallback to the regex based extraction
-    if matches = DYNAMIC_PATH_PATTERN.match(value.path)
+    if matches = self.class.extract_dynamic_path(value.path)
       @secret = matches[:secret]
       @identifier = matches[:identifier]
     end

lib/gitlab/import_export/uploads_manager.rb

@@ -43,12 +43,7 @@ def restore
       private
 
       def add_upload(upload)
-        secret, identifier = upload.split('/').last(2)
-
-        uploader_context = {
-          secret: secret,
-          identifier: identifier
-        }
+        uploader_context = FileUploader.extract_dynamic_path(upload).named_captures.symbolize_keys
 
         UploadService.new(@project, File.open(upload, 'r'), FileUploader, uploader_context).execute
       end

spec/lib/gitlab/import_export/uploads_manager_spec.rb

@@ -64,8 +64,8 @@
           stub_feature_flags(import_export_object_storage: true)
           stub_uploads_object_storage(FileUploader)
 
-          FileUtils.mkdir_p(File.join(shared.export_path, 'uploads/random'))
-          FileUtils.touch(File.join(shared.export_path, 'uploads/random', "dummy.txt"))
+          FileUtils.mkdir_p(File.join(shared.export_path, 'uploads/72a497a02fe3ee09edae2ed06d390038'))
+          FileUtils.touch(File.join(shared.export_path, 'uploads/72a497a02fe3ee09edae2ed06d390038', "dummy.txt"))
         end
 
         it 'restores the file' do

spec/uploaders/file_uploader_spec.rb

@@ -124,6 +124,15 @@ def store_dir
     end
   end
 
+  describe '.extract_dynamic_path' do
+    it 'works with hashed storage' do
+      path = 'export/4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a/test/uploads/72a497a02fe3ee09edae2ed06d390038/dummy.txt'
+
+      expect(described_class.extract_dynamic_path(path)[:identifier]).to eq('dummy.txt')
+      expect(described_class.extract_dynamic_path(path)[:secret]).to eq('72a497a02fe3ee09edae2ed06d390038')
+    end
+  end
+
   describe '#secret' do
     it 'generates a secret if none is provided' do
       expect(described_class).to receive(:generate_secret).and_return('secret')