Merge branch 'zj-repo-checksum-opt-out' into 'master'

Compute repository checksum by default

Closes gitaly#1146

See merge request gitlab-org/gitlab-ce!18648

changelogs/unreleased/zj-repo-checksum-opt-out.yml

+---
+title: Compute Gitlab::Git::Repository#checksum on Gitaly by default
+merge_request:
+author:
+type: performance

lib/gitlab/git/repository.rb

@@ -1569,7 +1569,8 @@ module Gitlab
       end
       def checksum
-        gitaly_migrate(:calculate_checksum) do |is_enabled|
+        gitaly_migrate(:calculate_checksum,
+                      status: Gitlab::GitalyClient::MigrationStatus::OPT_OUT) do |is_enabled|
           if is_enabled
             gitaly_repository_client.calculate_checksum
           else