commit - 31490d6b2395abd4459f794863b205b8358978fa
commit + 55f151dd04897f8d20a8c7e3a5a4ff89d6f1cfc4
blob - 168e28f0da1198afd1fbb89e87ebedda13f17406
blob + 3e42df1110827c2d294370cb448591d31dc71c55
--- dulwich/client.py
+++ dulwich/client.py
@@ -2181,7 +2181,7 @@ class Urllib3HttpGitClient(AbstractHttpGitClient):
         if username is not None:
             # No escaping needed: ":" is not allowed in username:
             # https://tools.ietf.org/html/rfc2617#section-2
-            credentials = "%s:%s" % (username, password)
+            credentials = f"{username}:{password or ''}"
             import urllib3.util
 
             basic_auth = urllib3.util.make_headers(basic_auth=credentials)
blob - 12f62d15e3ef2f408dc60a906e06e474720ff45a
blob + 767fe94a49c684c5c481bf515a8b19c4892dfe1c
--- dulwich/tests/test_client.py
+++ dulwich/tests/test_client.py
@@ -1020,7 +1020,20 @@ class HttpGitClientTests(TestCase):
         b64_credentials = base64.b64encode(auth_string.encode("latin1"))
         expected_basic_auth = "Basic %s" % b64_credentials.decode("latin1")
         self.assertEqual(basic_auth, expected_basic_auth)
+
+    def test_init_username_set_no_password(self):
+        url = "https://github.com/jelmer/dulwich"
 
+        c = HttpGitClient(url, config=None, username="user")
+        self.assertEqual("user", c._username)
+        self.assertIs(c._password, None)
+
+        basic_auth = c.pool_manager.headers["authorization"]
+        auth_string = b"user:"
+        b64_credentials = base64.b64encode(auth_string)
+        expected_basic_auth = f"Basic {b64_credentials.decode('ascii')}"
+        self.assertEqual(basic_auth, expected_basic_auth)
+
     def test_init_no_username_passwd(self):
         url = "https://github.com/jelmer/dulwich"
 
@@ -1029,6 +1042,20 @@ class HttpGitClientTests(TestCase):
         self.assertIs(None, c._password)
         self.assertNotIn("authorization", c.pool_manager.headers)
 
+    def test_from_parsedurl_username_only(self):
+        username = "user"
+        url = f"https://{username}@github.com/jelmer/dulwich"
+
+        c = HttpGitClient.from_parsedurl(urlparse(url))
+        self.assertEqual(c._username, username)
+        self.assertEqual(c._password, None)
+
+        basic_auth = c.pool_manager.headers["authorization"]
+        auth_string = username.encode('ascii') + b":"
+        b64_credentials = base64.b64encode(auth_string)
+        expected_basic_auth = f"Basic {b64_credentials.decode('ascii')}"
+        self.assertEqual(basic_auth, expected_basic_auth)
+
     def test_from_parsedurl_on_url_with_quoted_credentials(self):
         original_username = "john|the|first"
         quoted_username = urlquote(original_username)