Calculating repository checksums executed by Gitaly

OPT_OUT status has been removed, and alternative implementation removed.
Also checks if the repository exists before executing the checksum RPC
to guard against NotFound errors.

Closes gitlab-org/gitaly#1105

changelogs/unreleased/zj-calculate-checksum-mandator.yml

+---
+title: Remove shellout implementation for Repository checksums
+merge_request:
+author:
+type: other

lib/gitlab/git/repository.rb

@@ -1576,14 +1576,12 @@ module Gitlab
       end
 
       def checksum
-        gitaly_migrate(:calculate_checksum,
-                       status: Gitlab::GitalyClient::MigrationStatus::OPT_OUT) do |is_enabled|
-          if is_enabled
+        # The exists? RPC is much cheaper, so we perform this request first
+        raise NoRepository, "Repository does not exists" unless exists?
+
         gitaly_repository_client.calculate_checksum
-          else
-            calculate_checksum_by_shelling_out
-          end
-        end
+      rescue GRPC::NotFound
+        raise NoRepository # Guard against data races.
       end
 
       private
@@ -2498,36 +2496,6 @@ module Gitlab
         rev_parse_target(ref).oid
       end
 
-      def calculate_checksum_by_shelling_out
-        raise NoRepository unless exists?
-
-        args = %W(--git-dir=#{path} show-ref --heads --tags)
-        output, status = run_git(args)
-
-        if status.nil? || !status.zero?
-          # 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")
-
-        result = refs.inject(nil) do |checksum, ref|
-          value = Digest::SHA1.hexdigest(ref).hex
-
-          if checksum.nil?
-            value
-          else
-            checksum ^ value
-          end
-        end
-
-        result.to_s(16)
-      end
-
       def build_git_cmd(*args)
         object_directories = alternate_object_directories.join(File::PATH_SEPARATOR)
 

spec/lib/gitlab/git/repository_spec.rb

@@ -2247,7 +2247,6 @@ describe Gitlab::Git::Repository, seed_helper: true do
   end
 
   describe '#checksum' do
-    shared_examples 'calculating checksum' do
     it 'calculates the checksum for non-empty repo' do
       expect(repository.checksum).to eq '54f21be4c32c02f6788d72207fa03ad3bce725e4'
     end
@@ -2287,29 +2286,6 @@ describe Gitlab::Git::Repository, seed_helper: true do
     end
   end
 
-    context 'when calculate_checksum Gitaly feature is enabled' do
-      it_behaves_like 'calculating checksum'
-    end
-
-    context 'when calculate_checksum Gitaly feature is disabled', :disable_gitaly do
-      it_behaves_like 'calculating checksum'
-
-      describe 'when storage is broken', :broken_storage  do
-        it 'raises a storage exception when storage is not available' do
-          broken_repo = described_class.new('broken', 'a/path.git', '')
-
-          expect { broken_repo.rugged }.to raise_error(Gitlab::Git::Storage::Inaccessible)
-        end
-      end
-
-      it "raises a Gitlab::Git::Repository::Failure error if the `popen` call to git returns a non-zero exit code" do
-        allow(repository).to receive(:popen).and_return(['output', nil])
-
-        expect { repository.checksum }.to raise_error Gitlab::Git::Repository::ChecksumError
-      end
-    end
-  end
-
   context 'gitlab_projects commands' do
     let(:gitlab_projects) { repository.gitlab_projects }
     let(:timeout) { Gitlab.config.gitlab_shell.git_timeout }