Properly support local directories

We don't need git!

repo2docker/app.py

@@ -145,7 +145,7 @@ class Repo2Docker(Application):
 
         argparser.add_argument(
             'repo',
-            help='Path to repository that should be built'
+            help='Path to repository that should be built. Could be local path or a git URL.'
         )
 
         argparser.add_argument(
@@ -153,6 +153,11 @@ class Repo2Docker(Application):
             help='Name of image to be built. If unspecified will be autogenerated'
         )
 
+        argparser.add_argument(
+            '--ref',
+            help='If building a git url, which ref to check out'
+        )
+
         argparser.add_argument(
             '--push',
             dest='push',
@@ -180,11 +185,15 @@ class Repo2Docker(Application):
 
         self.load_config_file(args.config)
 
-        if '@' in args.repo:
-            self.repo, self.ref = args.repo.split('@', 1)
-        else:
+        if os.path.exists(args.repo):
+            # Let's treat this as a local directory we are building
+            self.repo_type = 'local'
             self.repo = args.repo
             self.ref = None
+        else:
+            self.repo_type = 'remote'
+            self.repo = args.repo
+            self.ref = args.ref
 
         if args.json_logs:
             # Need to reset existing handlers, or we repeat messages
@@ -207,7 +216,7 @@ class Repo2Docker(Application):
         else:
             # Attempt to set a sane default!
             # HACK: Provide something more descriptive?
-            self.output_image_spec = 'image-' + escapism.escape(self.repo).lower()
+            self.output_image_spec = 'r2d' + escapism.escape(self.repo, escape_char='-').lower() + str(int(time.time()))
 
         self.push = args.push
         self.run = args.run
@@ -278,12 +287,15 @@ class Repo2Docker(Application):
         return port
 
     def start(self):
-        checkout_path = os.path.join(self.git_workdir, str(uuid.uuid4()))
-        self.fetch(
-            self.repo,
-            self.ref,
-            checkout_path
-        )
+        if self.repo_type == 'local':
+            checkout_path = self.repo
+        else:
+            checkout_path = os.path.join(self.git_workdir, str(uuid.uuid4()))
+            self.fetch(
+                self.repo,
+                self.ref,
+                checkout_path
+            )
 
         os.chdir(checkout_path)
         for bp_spec in self.buildpacks:
@@ -302,7 +314,7 @@ class Repo2Docker(Application):
         else:
             raise Exception("No builder found!")
 
-        if self.cleanup_checkout:
+        if self.repo_type != 'local' and self.cleanup_checkout:
             shutil.rmtree(checkout_path)
 
         if self.push: