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mvn -Pgenerate -Ddatabase=${database} postgres clean package
That command produces the datafiles in activiti-upgrade/src/test/resources/org/activiti/db/${newVersionproject.version}/data. If you do this before you branched the code, bear Bear in mind that the default directory name might contains is based on the project version, which might contain the -SNAPSHOT. Then you can just manually change the directory name of the version.
If you want to produce new data files for older versions, use the upgradeVersion property like this
mvn -Pgenerate -Ddatabase=postgres -DupgradeVersion=5.8 clean package
Run that generate profile for every database.
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