The script relies on the (currently undocumented) dbuild behavior that properties files specified earlier in the list will take precedence. This is a bit unusual actually, and I would like to reverse it and document it as such in a later dbuild version (as in: later properties files take precedence).
My suggestion would be to use just:
```
properties: [
  "file:versions.properties"
  ${SBT_VERSION_PROPERTIES_FILE}
]
```
(always requiring the file to be specified). As long as there are no common properties in the two files, this will still work once the parsing order of properties files is reversed.