Formatting; clarify that this is just for basic authentication.

docs/tutorial/porcelain.txt

@@ -25,9 +25,12 @@ Clone a repository
 
   >>> porcelain.clone("git://github.com/jelmer/dulwich", "dulwich-clone")
   
-Authentication works using the ``username`` and ``password`` parameters:
+Basic uthentication works using the ``username`` and ``password`` parameters:
 
-  >>> porcelain.clone("https://example.com/a-private-repo.git", "a-private-repo-clone", username="user", password="password")
+  >>> porcelain.clone(
+      "https://example.com/a-private-repo.git",
+      "a-private-repo-clone",
+      username="user", password="password")
 
 Commit changes
 --------------