store: skip decodir check if path does not contain '.hg/'

The three replace calls are slower than this simple __contains__,
and anyway we should not have this many paths ending with .i, .d, or .hg
compared to the normal, un-encoded other paths.

mercurial/store.py

@@ -22,7 +22,7 b' def encodedir(path):'
             .replace(".d/", ".d.hg/"))
 
 def decodedir(path):
-    if not path.startswith('data/'):
+    if not path.startswith('data/') or ".hg/" not in path:
         return path
     return (path
             .replace(".d.hg/", ".d/")