bt5: adding manifest for bt5 speedup upgrading proccess
If the *Item objects will be not recreated during building process this would not work

diff -r b45deef68fac products/ERP5/Document/BusinessTemplate.py
--- a/products/ERP5/Document/BusinessTemplate.py	Thu Sep 18 17:28:45 2008 +0400
+++ b/products/ERP5/Document/BusinessTemplate.py	Thu Sep 18 17:50:08 2008 +0400
@@ -131,6 +131,11 @@
   for subobj in obj.objectValues():
     _recursiveRemoveUid(subobj)
 
+import md5
+def hash_hexdigest(str):
+  "hash function which are used for objects' checksums calculating"
+  return md5.md5(str).digest()
+
 def removeAll(entry):
   warn('removeAll is deprecated; use shutil.rmtree instead.',
        DeprecationWarning)
@@ -359,6 +364,7 @@
     self.__dict__.update(kw)
     self._archive = PersistentMapping()
     self._objects = PersistentMapping()
+    self._manifest = PersistentMapping() # for accumulating objects' checksums (hashes)
     for id in id_list:
       if id is not None and id != '':
         self._archive[id] = None
@@ -380,10 +386,14 @@
       new_keys = self._objects.keys()
       for path in new_keys:
         if installed_bt._objects.has_key(path):
-          # compare object to see if there are differences
-          new_obj_xml = self.generateXml(path=path)
-          old_obj_xml = installed_bt.generateXml(path=path, remove_properties=True)
-          if new_obj_xml != old_obj_xml:
+          try:
+            modified = self._manifest[path] != installed_bt._manifest[path]
+          except KeyError:
+            # compare object to see if there are differences
+            new_obj_xml = self.generateXml(path=path)
+            old_obj_xml = installed_bt.generateXml(path=path, remove_properties=True)
+            modified = new_obj_xml != old_obj_xml
+          if modified:
             modified_object_list.update({path : ['Modified', self.__class__.__name__[:-12]]})
           # else, compared versions are identical, don't overwrite the old one
         else: # new object
@@ -606,7 +616,12 @@
     else:
       obj = connection.importFile(file_obj, customImporters=customImporters)
     self.removeProperties(obj)
-    self._objects[file_name[:-4]] = obj
+    path=file_name[:-4]
+    self._objects[path] = obj
+
+    # adding checksum for this path
+    file_obj.seek(0)
+    self._manifest[path] = hash_hexdigest(file_obj.read())
 
   def generateXml(self, path, remove_properties=False, **kw):
     obj = self._objects[path]
@@ -5568,3 +5583,5 @@
 #     LOG('abort TM', 0, '')
 #     pass
 
+# vim: filetype=python syntax=python shiftwidth=2 softtabstop=2
+