Log base64-decoded PostReceive arguments

The change to base64-encoding the third argument to PostReceive in
gitlab-shell made our Sidekiq ArgumentsLogger a little less useful.
This change adds a log statement for the decoded data.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/20381

app/workers/post_receive.rb

@@ -10,6 +10,10 @@ class PostReceive
       log("Check gitlab.yml config for correct repositories.storages values. No repository storage path matches \"#{repo_path}\"")
     end
+    changes = Base64.decode64(changes) unless changes.include?(' ')
+    # Use Sidekiq.logger so arguments can be correlated with execution
+    # time and thread ID's.
+    Sidekiq.logger.info "changes: #{changes.inspect}" if ENV['SIDEKIQ_LOG_ARGUMENTS']
     post_received = Gitlab::GitPostReceive.new(repo_path, identifier, changes)
     if post_received.project.nil?

lib/gitlab/git_post_receive.rb

@@ -39,7 +39,6 @@ module Gitlab
     end
     def deserialize_changes(changes)
-      changes = Base64.decode64(changes) unless changes.include?(' ')
       changes = utf8_encode_changes(changes)
       changes.lines
     end