When you migrate from Plone 4 to Plone 5 and your default content types are converted from Archetypes to Dexterity (plone.app.contenttypes), all history information and previous revisions are deleted.
For some organisations this can be a deal breaker. Has anybody looked into preserving (part of) the history on objects. I’m well aware that technically very difficult, because CMFEditions stores a pickled version of the old content object, restoring these is not something you want. But the changelog is also lost (who changed something when), and I think most of the value of the revisions is for text/wysiwyg fields anyway. Relations etc. are an even bigger problem.
A best effort solution could be to store a ‘light’ DX version of at least primay/text fields from the older revisions of an object, skip references and converting it into a dexterity type so that the portal difftool can still show changes made, but strictly disallow reverting to the older object/revision. the migration time would double/triple/etc also for any extra older revision you’d want to store.
I’ve only looked at the included migrations of the @@atct_migrator. Is there any experience with transmogrifier migrations that do preserve history/revisions?