Add --label command line option

repo2docker/__main__.py

@@ -204,6 +204,14 @@ def get_argparser():
 
     argparser.add_argument("--appendix", type=str, help=Repo2Docker.appendix.help)
 
+    argparser.add_argument(
+        "--label",
+        dest="labels",
+        action="append",
+        help="Extra label to set on the image, in form name=value",
+        default=[],
+    )
+
     argparser.add_argument("--subdir", type=str, help=Repo2Docker.subdir.help)
 
     argparser.add_argument(
@@ -246,6 +254,13 @@ def make_r2d(argv=None):
     if args.appendix:
         r2d.appendix = args.appendix
 
+    for l in args.labels:
+        if "=" in l:
+            key, val = l.split("=", 1)
+            r2d.labels[key] = val
+        else:
+            r2d.labels[l] = ""
+
     r2d.repo = args.repo
     r2d.ref = args.ref
 

repo2docker/app.py

@@ -237,6 +237,17 @@ class Repo2Docker(Application):
         """,
     )
 
+    labels = Dict(
+        {},
+        help="""
+        Extra labels to set on the final image.
+
+        Each Label is a key-value pair, with the key being the name of the label
+        and the value its value.
+        """,
+        config=True,
+    )
+
     json_logs = Bool(
         False,
         help="""
@@ -747,6 +758,8 @@ class Repo2Docker(Application):
                 picked_buildpack.labels["repo2docker.repo"] = repo_label
                 picked_buildpack.labels["repo2docker.ref"] = self.ref
 
+                picked_buildpack.labels.update(self.labels)
+
                 if self.dry_run:
                     print(picked_buildpack.render())
                 else: