url: fix crash by empty path with #fragments

Before, "#foo" paths made hg crash. We've moved the #fragment parsing at
64fbd0de9773, but we shouldn't set path to None too early. This patch just
removes the "if not path:" block since that's checked a few lines later.

mercurial/util.py

@@ -2377,6 +2377,22 b' class url(object):'
     <url scheme: 'http', host: 'host', path: 'a', query: 'b', fragment: 'c'>
     >>> url('http://host/a?b#c', parsequery=False, parsefragment=False)
     <url scheme: 'http', host: 'host', path: 'a?b#c'>
+
+    Empty path:
+
+    >>> url('')
+    <url path: ''>
+    >>> url('#a')
+    <url path: '', fragment: 'a'>
+    >>> url('http://host/')
+    <url scheme: 'http', host: 'host', path: ''>
+    >>> url('http://host/#a')
+    <url scheme: 'http', host: 'host', path: '', fragment: 'a'>
+
+    Only scheme:
+
+    >>> url('http:')
+    <url scheme: 'http'>
     """
 
     _safechars = "!~*'()+"
@@ -2393,8 +2409,6 b' class url(object):'
 
         if parsefragment and '#' in path:
             path, self.fragment = path.split('#', 1)
-            if not path:
-                path = None
 
         # special case for Windows drive letters and UNC paths
         if hasdriveletter(path) or path.startswith(r'\\'):

tests/test-url-rev.t

@@ -320,3 +320,12 b' Test handling common incoming revisions '
   remote: 1 outgoing
 
   $ cd ..
+
+Test url#rev syntax of local destination path, which should be taken as
+a 'url#rev' path
+
+  $ hg clone repo '#foo'
+  updating to branch default
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg root -R '#foo'
+  $TESTTMP/#foo (glob)