Faster cache in find (#561)

* use dict instead of list

* convert cache dicts back to list

gcsfs/core.py

@@ -1254,15 +1254,17 @@ async def _find(
                     "size": 0,
                 }
 
-                listing = cache_entries.setdefault(parent, [])
-                if previous not in listing:
-                    listing.append(previous)
+                listing = cache_entries.setdefault(parent, {})
+                name = previous["name"]
+                if name not in listing:
+                    listing[name] = previous
 
                 previous = dirs[parent]
                 parent = self._parent(parent)
 
         if not prefix:
-            self.dircache.update(cache_entries)
+            cache_entries_list = {k: list(v.values()) for k, v in cache_entries.items()}
+            self.dircache.update(cache_entries_list)
 
         if withdirs:
             objects = sorted(objects + list(dirs.values()), key=lambda x: x["name"])