Resolve fetch urls more efficiently

Instead of using regex, append the netloc and relative
scheme lists with the custom scheme.
The schemes will only be appended when needed, instead
of passing X amount of regex replaces.

see http://bugs.python.org/issue18828 for more details.

Change-Id: I10d26d5ddc32e7ed04c5a412bdd6e13ec59eb70f

manifest_xml.py

@@ -38,8 +38,9 @@ MANIFEST_FILE_NAME = 'manifest.xml'
 LOCAL_MANIFEST_NAME = 'local_manifest.xml'
 LOCAL_MANIFESTS_DIR_NAME = 'local_manifests'
 
-urllib.parse.uses_relative.extend(['ssh', 'git'])
-urllib.parse.uses_netloc.extend(['ssh', 'git'])
+# urljoin gets confused if the scheme is not known.
+urllib.parse.uses_relative.extend(['ssh', 'git', 'persistent-https', 'rpc'])
+urllib.parse.uses_netloc.extend(['ssh', 'git', 'persistent-https', 'rpc'])
 
 class _Default(object):
   """Project defaults within the manifest."""
@@ -85,21 +86,13 @@ class _XmlRemote(object):
     # urljoin will gets confused over quite a few things.  The ones we care
     # about here are:
     # * no scheme in the base url, like <hostname:port>
-    # * persistent-https://
-    # * rpc://
-    # We handle this by replacing these with obscure protocols
-    # and then replacing them with the original when we are done.
-    # gopher -> <none>
-    # wais -> persistent-https
-    # nntp -> rpc
+    # We handle no scheme by replacing it with an obscure protocol, gopher
+    # and then replacing it with the original when we are done.
+
     if manifestUrl.find(':') != manifestUrl.find('/') - 1:
-      manifestUrl = 'gopher://' + manifestUrl
-    manifestUrl = re.sub(r'^persistent-https://', 'wais://', manifestUrl)
-    manifestUrl = re.sub(r'^rpc://', 'nntp://', manifestUrl)
-    url = urllib.parse.urljoin(manifestUrl, url)
-    url = re.sub(r'^gopher://', '', url)
-    url = re.sub(r'^wais://', 'persistent-https://', url)
-    url = re.sub(r'^nntp://', 'rpc://', url)
+      url = urllib.parse.urljoin('gopher://' + manifestUrl, url)[9:]
+    else:
+      url = urllib.parse.urljoin(manifestUrl, url)
     return url
 
   def ToRemoteSpec(self, projectName):