Print message to $stderr for custom action

lib/action/custom.rb

@@ -54,6 +54,8 @@ module Action
           raise UnsuccessfulError, 'Response was not valid JSON'
         end
 
+        inform_client(body['message']) if body['message']
+
         print_flush(body['result'])
 
         # In the context of the git push sequence of events, it's necessary to read
@@ -94,6 +96,10 @@ module Action
       $stdout.flush
     end
 
+    def inform_client(str)
+      $stderr.puts(str)
+    end
+
     def validate!
       validate_payload!
       validate_data!

spec/action/custom_spec.rb

@@ -52,6 +52,12 @@ describe Action::Custom do
               allow($stdout).to receive(:print).with('push-result')
             end
 
+            it 'prints a message to $stderr' do
+              VCR.use_cassette("custom-action-ok-with-message") do
+                expect { subject.execute }.to output(/NOTE: Message here/).to_stderr
+              end
+            end
+
             it 'returns an instance of Net::HTTPCreated' do
               VCR.use_cassette("custom-action-ok") do
                 expect(subject.execute ).to be_instance_of(Net::HTTPCreated)

spec/vcr_cassettes/custom-action-ok-with-message.yml

+---
+http_interactions:
+- request:
+    method: post
+    uri: http://localhost:3000/api/v4/fake/info_refs
+    body:
+      encoding: UTF-8
+      string: '{"data":{"gl_username":"user1","primary_repo":"http://localhost:3001/user1/repo1.git","gl_id":"key-1"},"output":"","secret_token":"0a3938d9d95d807e94d937af3a4fbbea"}'
+    headers:
+      Content-Type:
+      - application/json
+      Accept-Encoding:
+      - gzip;q=1.0,deflate;q=0.6,identity;q=0.3
+      Accept:
+      - "*/*"
+      User-Agent:
+      - Ruby
+      Host:
+      - localhost
+  response:
+    status:
+      code: 200
+      message: OK
+    headers:
+      Date:
+      - Fri, 20 Jul 2018 06:18:58 GMT
+      Connection:
+      - close
+      X-Frame-Options:
+      - SAMEORIGIN
+      X-Content-Type-Options:
+      - nosniff
+      Content-Type:
+      - application/json
+      Content-Length:
+      - '172'
+      Vary:
+      - Origin
+      Etag:
+      - W/"7d01e1e3dbcbe7cca9607461352f8244"
+      Cache-Control:
+      - max-age=0, private, must-revalidate
+      X-Request-Id:
+      - 03afa234-b6be-49ab-9392-4aa35c5dee25
+      X-Runtime:
+      - '1.436040'
+    body:
+      encoding: UTF-8
+      string: '{"result":"aW5mb19yZWZzLXJlc3VsdA==\n", "message":"NOTE: Message here"}'
+    http_version:
+  recorded_at: Fri, 20 Jul 2018 06:18:58 GMT
+- request:
+    method: post
+    uri: http://localhost:3000/api/v4/fake/push
+    body:
+      encoding: UTF-8
+      string: '{"data":{"gl_username":"user1","primary_repo":"http://localhost:3001/user1/repo1.git","gl_id":"key-1"},"output":"info_refs-result","secret_token":"0a3938d9d95d807e94d937af3a4fbbea"}'
+    headers:
+      Content-Type:
+      - application/json
+      Accept-Encoding:
+      - gzip;q=1.0,deflate;q=0.6,identity;q=0.3
+      Accept:
+      - "*/*"
+      User-Agent:
+      - Ruby
+      Host:
+      - localhost
+  response:
+    status:
+      code: 201
+      message: Created
+    headers:
+      Date:
+      - Fri, 20 Jul 2018 06:19:08 GMT
+      Connection:
+      - close
+      X-Frame-Options:
+      - SAMEORIGIN
+      X-Content-Type-Options:
+      - nosniff
+      Content-Type:
+      - application/json
+      Content-Length:
+      - '13'
+      Vary:
+      - Origin
+      Cache-Control:
+      - no-cache
+      X-Request-Id:
+      - 0c6894ac-7f8e-4cdb-871f-4cb64d3731ca
+      X-Runtime:
+      - '0.786754'
+    body:
+      encoding: UTF-8
+      string: '{"result":"cHVzaC1yZXN1bHQ=\n"}'
+    http_version:
+  recorded_at: Fri, 20 Jul 2018 06:19:08 GMT
+recorded_with: VCR 2.4.0