add slash_join helper and tests

test/test_util.py

@@ -6,6 +6,7 @@ from semantic_version import Version, Spec
 from util.validation import generate_valid_usernames
 from util.registry.generatorfile import GeneratorFile
 from util.registry.dockerver import docker_version
+from util.string import slash_join
 
 class TestGeneratorFile(unittest.TestCase):
   def sample_generator(self):
@@ -174,6 +175,21 @@ class TestDockerVersionParsing(unittest.TestCase):
         self.assertTrue(spec.match(Version(match_case)),
                         'Spec: %s Case: %s' % (spec, match_case))
 
+
+class TestSlashJoining(unittest.TestCase):
+  def test_joining(self):
+    test_cases = [
+      (['https://github.com', '/coreos-inc/' 'quay/pull/1092/files'],
+       'https://github.com/coreos-inc/quay/pull/1092/files'),
+      (['https://', 'github.com/', '/coreos-inc', '/quay/pull/1092/files/'],
+       'https://github.com/coreos-inc/quay/pull/1092/files'),
+    ]
+
+    for args, url in test_cases:
+      joined_url = slash_join(*args)
+      self.assertEquals(url, joined_url)
+
+
 if __name__ == '__main__':
   unittest.main()
 

util/string.py

@@ -0,0 +1,13 @@
+def slash_join(*args):
+  """
+  Joins together strings and guarantees there is only one '/' in between the
+  each string joined. Double slashes ('//') are assumed to be intentional and
+  are not deduplicated.
+  """
+  def rmslash(path):
+    path = path[1:] if path[0] == '/' else path
+    path = path[:-1] if path[-1] == '/' else path
+    return path
+
+  args = [rmslash(path) for path in args]
+  return '/'.join(args)