Allow console messages be sent to gitlab-shell

gl_console_messages is now returned in the
payload that is processed by gitlab-shell and
will be printed to $stderr if present.

lib/api/internal.rb

@@ -87,7 +87,8 @@ module API
             gl_id: Gitlab::GlId.gl_id(user),
             gl_username: user&.username,
             git_config_options: [],
-            gitaly: gitaly_payload(params[:action])
+            gitaly: gitaly_payload(params[:action]),
+            gl_console_messages: check_result.console_messages
           }
 
           # Custom option for git-receive-pack command

lib/gitlab/git_access.rb

@@ -85,7 +85,7 @@ module Gitlab
         check_push_access!
       end
 
-      ::Gitlab::GitAccessResult::Success.new
+      ::Gitlab::GitAccessResult::Success.new(console_messages: check_for_console_messages(cmd))
     end
 
     def guest_can_download_code?
@@ -116,6 +116,10 @@ module Gitlab
       nil
     end
 
+    def check_for_console_messages(cmd)
+      []
+    end
+
     def check_valid_actor!
       return unless actor.is_a?(Key)
 

lib/gitlab/git_access_result/success.rb

@@ -3,6 +3,11 @@
 module Gitlab
   module GitAccessResult
     class Success
+      attr_reader :console_messages
+
+      def initialize(console_messages: [])
+        @console_messages = console_messages
+      end
     end
   end
 end

spec/requests/api/internal_spec.rb

@@ -498,6 +498,40 @@ describe API::Internal do
       end
     end
 
+    context "console message" do
+      before do
+        project.add_developer(user)
+      end
+
+      context "git pull" do
+        context "with no console message" do
+          it "has the correct payload" do
+            pull(key, project)
+
+            expect(response).to have_gitlab_http_status(200)
+            expect(json_response['gl_console_messages']).to eq([])
+          end
+        end
+
+        context "with a console message" do
+          let(:console_messages) { ['message for the console'] }
+
+          it "has the correct payload" do
+            expect_next_instance_of(Gitlab::GitAccess) do |access|
+              expect(access).to receive(:check_for_console_messages)
+                                  .with('git-upload-pack')
+                                  .and_return(console_messages)
+            end
+
+            pull(key, project)
+
+            expect(response).to have_gitlab_http_status(200)
+            expect(json_response['gl_console_messages']).to eq(console_messages)
+          end
+        end
+      end
+    end
+
     context "blocked user" do
       let(:personal_project) { create(:project, namespace: user.namespace) }