2011-11-23: better comment

better comment

diff --git a/site.py b/site.py
--- a/site.py
+++ b/site.py
@@ -390,7 +390,7 @@ def upload(ui, repo, target, ftpstring, 
                             ui.warn(_("could not create directory "),
                                     sd, ": " , resp, "\n")
 
-                if not serverfile in _ftplistcache: # should happen only once per dir.
+                if not serverfile in _ftplistcache: # should happen for existing files only once per dir.
                     _ftplistcache.update(set(ftp.nlst(serverdir)))
                 if not serverfile in _ftplistcache or force:
                     if force: