--- a/commitwatcher/store.py	Sat Sep 28 20:33:17 2013 -0700
+++ b/commitwatcher/store.py	Sun Sep 29 20:23:51 2013 -0700
@@ -15,11 +15,23 @@
     def paths(self, *commits):
         """return all paths touched for a given commit"""
 
+    def ancestry(self, path):
+        sep = '/' # unix/url-style separators
+        path = path.split('/')
+        paths = []
+        while path:
+            paths.append(sep.join(path))
+            path.pop()
+        return paths
+
 
 class MemoryStore(CommitStore):
     """store in volatile memory"""
     # volatile!
 
+    def __init__(self):
+        self.path_to_commit = {}
+
     def add(self, commit):
         raise NotImplementedError()
 
@@ -27,3 +39,9 @@
         """
         return touched by commits
         """
+
+        paths = set()
+        for commit in commits:
+            for f in commit.files:
+                
+                raise NotImplementedError