Raise InvalidRepository error for non-valid git repositories

lib/gitlab/git/repository.rb

@@ -30,6 +30,7 @@ module Gitlab
       EMPTY_REPOSITORY_CHECKSUM = '0000000000000000000000000000000000000000'.freeze
       NoRepository = Class.new(StandardError)
+      InvalidRepository = Class.new(StandardError)
       InvalidBlobName = Class.new(StandardError)
       InvalidRef = Class.new(StandardError)
       GitError = Class.new(StandardError)
@@ -1584,7 +1585,7 @@ module Gitlab
       def checksum
         gitaly_migrate(:calculate_checksum,
-                      status: Gitlab::GitalyClient::MigrationStatus::OPT_OUT) do |is_enabled|
+                       status: Gitlab::GitalyClient::MigrationStatus::OPT_OUT) do |is_enabled|
           if is_enabled
             gitaly_repository_client.calculate_checksum
           else
@@ -2533,10 +2534,12 @@ module Gitlab
         output, status = run_git(args)
         if status.nil? || !status.zero?
-          # Empty repositories return with a non-zero status and an empty output.
-          return EMPTY_REPOSITORY_CHECKSUM if output&.empty?
-          raise ChecksumError, output
+          # Non-valid git repositories return 128 as the status code and an error output
+          raise InvalidRepository if status == 128 && output.to_s.downcase =~ /not a git repository/
+          # Empty repositories returns with a non-zero status and an empty output.
+          raise ChecksumError, output unless output.blank?
+          return EMPTY_REPOSITORY_CHECKSUM
         end
         refs = output.split("\n")

lib/gitlab/gitaly_client/repository_service.rb

@@ -292,6 +292,8 @@ module Gitlab
         request  = Gitaly::CalculateChecksumRequest.new(repository: @gitaly_repo)
         response = GitalyClient.call(@storage, :repository_service, :calculate_checksum, request)
         response.checksum.presence
+      rescue GRPC::DataLoss => e
+        raise Gitlab::Git::Repository::InvalidRepository.new(e)
       end
       def raw_changes_between(from, to)

spec/lib/gitlab/git/repository_spec.rb

@@ -2275,7 +2275,22 @@ describe Gitlab::Git::Repository, seed_helper: true do
         expect(empty_repo.checksum).to eq '0000000000000000000000000000000000000000'
       end
-      it 'raises a no repository exception when there is no repo' do
+      it 'raises Gitlab::Git::Repository::InvalidRepository error for non-valid git repo' do
+        FileUtils.rm_rf(File.join(storage_path, 'non-valid.git'))
+
+        system(git_env, *%W(#{Gitlab.config.git.bin_path} clone --bare #{TEST_REPO_PATH} non-valid.git),
+               chdir: SEED_STORAGE_PATH,
+               out: '/dev/null',
+               err: '/dev/null')
+
+        File.truncate(File.join(storage_path, 'non-valid.git/HEAD'), 0)
+
+        non_valid = described_class.new('default', 'non-valid.git', '')
+
+        expect { non_valid.checksum }.to raise_error(Gitlab::Git::Repository::InvalidRepository)
+      end
+
+      it 'raises Gitlab::Git::Repository::NoRepository error when there is no repo' do
         broken_repo = described_class.new('default', 'a/path.git', '')
         expect { broken_repo.checksum }.to raise_error(Gitlab::Git::Repository::NoRepository)