lfs: ensure the transfer request is for a known URI

Since the dispatching code only checks the beginning of the string, this
enforces that there's only one more path component.

hgext/lfs/wireprotolfsserver.py

@@ -22,6 +22,7 b' from mercurial import ('
 HTTP_OK = hgwebcommon.HTTP_OK
 HTTP_CREATED = hgwebcommon.HTTP_CREATED
 HTTP_BAD_REQUEST = hgwebcommon.HTTP_BAD_REQUEST
+HTTP_NOT_FOUND = hgwebcommon.HTTP_NOT_FOUND
 
 def handlewsgirequest(orig, rctx, req, res, checkperm):
     """Wrap wireprotoserver.handlewsgirequest() to possibly process an LFS
@@ -244,6 +245,10 b' def _processbasictransfer(repo, req, res'
     oid = req.dispatchparts[-1]
     localstore = repo.svfs.lfslocalblobstore
 
+    if len(req.dispatchparts) != 4:
+        _sethttperror(res, HTTP_NOT_FOUND)
+        return True
+
     if method == b'PUT':
         checkperm('upload')