Enable override default headers from CLI

hyper/cli.py

@@ -164,7 +164,14 @@ def set_request_data(args):
     body, headers, params = {}, {}, {}
     for i in args.items:
         if i.sep == SEP_HEADERS:
-            headers[i.key] = i.value
+            if i.key:
+                headers[i.key] = i.value
+            else:
+                # when overriding a HTTP/2 special header there will be a leading 
+                # colon, which tricks the command line parser into thinking 
+                # the header is empty
+                k, v = i.value.split(':', 1)
+                headers[':' + k] = v
         elif i.sep == SEP_QUERY:
             params[i.key] = i.value
         elif i.sep == SEP_DATA:

test/test_cli.py

@@ -110,11 +110,20 @@ def test_cli_with_system_exit(argv):
      {'method': 'GET', 'url.path': '/?param=test'}),
     (['POST', 'example.com', 'data=test'],
      {'method': 'POST', 'body': '{"data": "test"}'}),
+    (['GET', 'example.com', ':authority:example.org'],
+     {'method': 'GET', 'headers': {
+                            ':authority': 'example.org'}}),
+    (['GET', 'example.com', ':authority:example.org', 'x-test:header'],
+     {'method': 'GET', 'headers': {
+                            ':authority': 'example.org',
+                            'x-test':'header'}}),
 ], ids=[
     'specified "--debug" option',
     'specified host and additional header',
     'specified host and get parameter',
     'specified host and post data',
+    'specified host and override default header',
+    'specified host and override default header and additional header',
 ])
 def test_parse_argument(argv, expected):
     args = parse_argument(argv)