Add Dockerfile repo2docker labels

repo2docker/app.py

@@ -745,6 +745,11 @@ class Repo2Docker(Application):
                     picked_buildpack = self.default_buildpack()
 
                 picked_buildpack.appendix = self.appendix
+                picked_buildpack.labels = {
+                    'repo2docker.version': self.version,
+                    'repo2docker.repo': self.repo,
+                    'repo2docker.ref': self.ref,
+                }
 
                 self.log.debug(picked_buildpack.render(),
                                extra=dict(phase='building'))

repo2docker/buildpacks/base.py

@@ -120,8 +120,8 @@ ENV {{item[0]}} {{item[1]}}
 # Container image Labels!
 # Put these at the end, since we don't want to rebuild everything
 # when these change! Did I mention I hate Dockerfile cache semantics?
-{% for k, v in labels.items() -%}
-LABEL {{k}}={{v}}
+{% for k, v in labels.items() %}
+LABEL {{k}}="{{v}}"
 {%- endfor %}
 
 # We always want containers to run as non-root
@@ -246,7 +246,7 @@ class BuildPack:
         """
         Docker labels to set on the built image.
         """
-        return {}
+        return getattr(self, 'labels', {})
 
     def get_build_script_files(self):
         """