Explicitly flush versions to disk on update

Fixes #4

data.py

@@ -124,12 +124,14 @@ class BsdDB:
         p = self.ctype (p)
         return p
 
-    def put (self, key, val):
+    def put (self, key, val, sync=False):
         key = autoBytes (key)
         val = autoBytes (val)
         if type (val) is not bytes:
             val = val.pack()
         self.db.put (key, val)
+        if sync:
+            self.db.sync()
 
 class DB:
     def __init__ (self, dir, readonly=True):

update.py

@@ -48,7 +48,7 @@ def updateVersions (tag):
     obj = PathList()
     for idx, path in buf:
         obj.append (idx, path)
-    db.vers.put (tag, obj)
+    db.vers.put (tag, obj, sync=True)
 
 def updateDefinitions (blobs):
     for blob in blobs: