Migration on PostgreSQL from an older version will cause many merge conflicts on DW

I tested a migration from 4.5.4 to 6.2M2.

Environment:

1. Mac OS X 10.9.4
2. Jetty 8.1.15
3. ProgreSQL 9.3.4

Steps to reproduce:

1. Create some (sub)wikis on 4.5.4, add users to them, write some comments, add attachments, annotations, pages, spaces etc.
2. Close the 4.5.4 and open 6.2M2
3. Login in to 6.2M2
4. When DW appears do not select that you know the version you are migrating for (in this case 4.5.4)
5. After the migrations start (after ~2 min.) the merge conflicts appear
6. Another problem I discovered:
   1. When you select "Compare"... "With", you are able to see just the "Current version" and "New version", no "Previous verion"
   2. In some cases, the new version is edited a few years ago (you will see on the attachments), compared with the current version

I've made the same steps on a migration using HyperSQL from 4.5.4 to 6.2M2 (I did not choose the version, I choose "I don't know the version") and the migrations worked ok.
On ProgreSQL are a lot of merge conflicts and after a hour and a half, the merge conflicts are still appear.

Merge conflicts examples:

1. Changes for document XWiki.Admin
2. Changes for document XWiki.XWikiAdminGroup
3. Changes for document XWiki.XWikiAllGroup
4. Changes for document XWiki.XWikiPreferences
5. Changes for document XWiki.AttachmentSelector
6. Changes for document XWiki.ConfigurableClassMacros
7. Changes for document XWiki.Registration
8. Changes for document XWiki.XWikiSkinsSheet
9. Changes for document XWiki.AdminTemplatesSheet
10. Changes for document XWiki.XWikiGroupSheet
11. Changes for document XWiki.AdminSheet
12. Changes for document XWiki.AdminUsersSheet
13. Changes for document XWiki.AdminFieldsDisplaySheet
14. Changes for document XWiki.AdminLocalizationSheet
15. Changes for document XWiki.AccountValidation
16. Changes for document XWiki.ResetPasswordMailContent
17. Changes for document XWiki.ForgotUsername
18. Changes for document XWiki.AdminGroupsSheet
19. Changes for document XWiki.AdminRegistrationSheet
20. Changes for document XWiki.AdminPresentationSheet
21. Changes for document XWiki.AdminInlineSheet
22. Changes for document XWiki.AdminElementsSheet
23. Changes for document XWiki.ConfigurableClass
24. Changes for document XWiki.AdminEmailSheet
25. Changes for document XWiki.GoogleAnalyticsCode
26. Changes for document XWiki.ResetPasswordComplete
27. Changes for document XWiki.DefaultSkin
28. Changes for document XWiki.RegistrationConfig
29. Changes for document XWiki.AdminEditingSheet
30. Changes for document XWiki.RegistrationHelp
31. Changes for document XWiki.ResetPassword
32. Changes for document XWiki.LiveTableResultsMacros
33. Changes for document XWiki.LiveTableResults
34. Changes for document Main.AllDocs
35. Changes for document Main.SpaceIndex
36. Changes for document XWiki.OrphanedPages
37. Changes for document XWiki.AllAttachmentsResults
38. Changes for document XWiki.DeletedAttachments
39. Changes for document XWiki.DeletedDocumentsJSON
40. Changes for document XWiki.Tableview
41. Changes for document XWiki.AllAttachments
42. Changes for document XWiki.DeletedDocuments
43. Changes for document XWiki.DocumentsMacro
44. Changes for document XWiki.Treeview
45. Changes for document Panels.PanelTemplate
46. Changes for document Panels.AddClassProperty
47. Changes for document Panels.ObjectEditorWelcome
48. Changes for document Panels.OrphanedPages
... and so on.