Add a minimal test for external toctree links and fix a small bug found by it.

sphinx/environment.py

@@ -1005,8 +1005,9 @@ class BuildEnvironment:
         _walk_depth(newnode, 1, prune and maxdepth or 0)
         # set the target paths in the toctrees (they are not known at TOC generation time)
         for refnode in newnode.traverse(nodes.reference):
-            refnode['refuri'] = builder.get_relative_uri(
-                docname, refnode['refuri']) + refnode['anchorname']
+            if not refnode['refuri'].startswith('http://'):  # FIXME: see above
+                refnode['refuri'] = builder.get_relative_uri(
+                    docname, refnode['refuri']) + refnode['anchorname']
         return newnode
 
     descroles = frozenset(('data', 'exc', 'func', 'class', 'const', 'attr', 'obj',

tests/root/contents.txt

@@ -18,6 +18,8 @@ Contents:
    math
    autodoc
 
+   Python <http://python.org/>
+
 Indices and tables
 ==================
 

tests/test_build.py

@@ -95,6 +95,7 @@ HTML_XPATH = {
         ".//li[@class='toctree-l2']/a": 'Admonitions',
         ".//title": 'Sphinx <Tests>',
         ".//div[@class='footer']": 'Georg Brandl & Team',
+        ".//a[@href='http://python.org/']": '',
     },
 }