Refactor snippet repo path error handling

app/models/snippet_repository.rb

@@ -7,6 +7,7 @@ class SnippetRepository < ApplicationRecord
   EMPTY_FILE_PATTERN = /^#{DEFAULT_EMPTY_FILE_NAME}(\d+)\.txt$/.freeze
 
   CommitError = Class.new(StandardError)
+  InvalidPathError = Class.new(CommitError)
 
   belongs_to :snippet, inverse_of: :snippet_repository
 
@@ -40,8 +41,9 @@ class SnippetRepository < ApplicationRecord
   rescue Gitlab::Git::Index::IndexError,
          Gitlab::Git::CommitError,
          Gitlab::Git::PreReceiveError,
-         Gitlab::Git::CommandError => e
-    raise CommitError, e.message
+         Gitlab::Git::CommandError => error
+
+    raise commit_error_exception(error)
   end
 
   def transform_file_entries(files)
@@ -85,4 +87,16 @@ class SnippetRepository < ApplicationRecord
   def build_empty_file_name(index)
     "#{DEFAULT_EMPTY_FILE_NAME}#{index}.txt"
   end
+
+  def commit_error_exception(error)
+    if error.is_a?(Gitlab::Git::Index::IndexError) && invalid_path_error?(error.message)
+      InvalidPathError.new('Invalid Path') # To avoid returning the message with the path included
+    else
+      CommitError.new(error.message)
+    end
+  end
+
+  def invalid_path_error?(message)
+    message.downcase.start_with?('invalid path', 'path cannot include directory traversal')
+  end
 end

lib/gitlab/background_migration/backfill_snippet_repositories.rb

@@ -117,7 +117,7 @@ module Gitlab
       # the migration can succeed, to achieve that, we'll identify in migration retries
       # that the path is invalid
       def set_file_path_error(error)
-        @invalid_path_error = error.message.downcase.start_with?('invalid path', 'path cannot include directory traversal')
+        @invalid_path_error = error.is_a?(SnippetRepository::InvalidPathError)
       end
     end
   end

spec/models/snippet_repository_spec.rb

@@ -202,6 +202,22 @@ describe SnippetRepository do
 
       it_behaves_like 'snippet repository with file names', 'snippetfile10.txt', 'snippetfile11.txt'
     end
+
+    shared_examples 'snippet repository with git errors' do |path, error|
+      let(:new_file) { { file_path: path, content: 'bar' } }
+
+      it 'raises a path specific error' do
+        expect do
+          snippet_repository.multi_files_action(user, data, commit_opts)
+        end.to raise_error(error)
+      end
+    end
+
+    context 'with git errors' do
+      it_behaves_like 'snippet repository with git errors', 'invalid://path/here', described_class::InvalidPathError
+      it_behaves_like 'snippet repository with git errors', '../../path/traversal/here', described_class::InvalidPathError
+      it_behaves_like 'snippet repository with git errors', 'README', described_class::CommitError
+    end
   end
 
   def blob_at(snippet, path)