I have templates from 1.1.4 and 1.1.5 in the style that was imported before 1.2 update. When I click merge changes I get an error „No previous version of the parent could be found. Merging is not possible.“. If I click „Automatically Merge Changes“ the page just refreshes.
So to fix this we just need to automatically create a new history record for all outdated templates.
No, you can't do that. The data simply isn't there or the data that is there doesn't apply.
If you want to recreate it retroactively, you need to do it by hand using the version of the template your edits are known to be "based on".
If the data isn't there, then this is totally expected behavior. There's no strict bug here unless the data isn't being kept when it should be (during the upgrade). Bear in mind my comment about the data being removed over time if these templates have been outdated for a while. When did you upgrade from 1.1 and has the style in question been imported via XML recently?
How can I figure out the data is in place? I have version numbers in outdated templates.
About 1.1 → 1.2. Board was upgraded to some beta release first, then to final 1.2. Can't give you exact beta versions unfortunately.
And style hasn't been imported or re-imported recently (I think about 2-3 months at least).
If it depends on last edit — they were done long time ago. But I don't understand why should it matter if I did all the upgrades right.
Nothing in the merging system is based on version numbers - it's based on relative edit dates.
You updated when 1.2.0 was released at the end of July?
So the templates have been out of date for over a month? If so, this would be expected. The old history data would have been removed based on the "Template History Length" option (which defaults to 30 days). The expectation is that updating templates is part of the upgrade process so they wouldn't stay outdated for that long. The templates can still be updated manually (revert and reapply changes or compare the differences between your templates and the current one).
Ok, but why all the history is removed? I thought it should save at least the last version. It still does the thing, but you also can auto-update templates no matter when.
This is not expected in just one thing: there is no explanation that expired templates can't be auto-updated.