hgweb: add hook for remapping repository path into virtual paths

Extensions such as largefiles can use this to remap files so they
appear in the same location as they do in the user's working copy.

mercurial/hgweb/webcommands.py

@@ -303,6 +303,14 b' def changeset(web, req, tmpl):'
 
 rev = changeset
 
+def decodepath(path):
+    """Hook for mapping a path in the repository to a path in the
+    working copy.
+
+    Extensions (e.g., largefiles) can override this to remap files in
+    the virtual file system presented by the manifest command below."""
+    return path
+
 def manifest(web, req, tmpl):
     ctx = webutil.changectx(web.repo, req)
     path = webutil.cleanpath(web.repo, req.form.get('file', [''])[0])
@@ -318,13 +326,17 b' def manifest(web, req, tmpl):'
     l = len(path)
     abspath = "/" + path
 
-    for f, n in mf.iteritems():
+    for full, n in mf.iteritems():
+        # the virtual path (working copy path) used for the full
+        # (repository) path
+        f = decodepath(full)
+
         if f[:l] != path:
             continue
         remain = f[l:]
         elements = remain.split('/')
         if len(elements) == 1:
-            files[remain] = f
+            files[remain] = full
         else:
             h = dirs # need to retain ref to dirs (root)
             for elem in elements[0:-1]: