Getdown does not auto-update correctly first time when jar filenames change

When a jar file changes name in the website appdir (e.g. https://www.jalview.org/getdown/release/1.8/release/intervalstore-1.0.jar to intervalstore-1.1.jar) an existing installation of Jalview that checks that appdir fails to launch the first time it tries after the update appears on the website. It displays an error saying:
"We were unable to download the necessary files after five attempts. You can try running the application again, but if it fails you may need to uninstall and reinstall"

In fact running the application again works.

The problem seems to be down to the list of code/resource files from the previous getdown.txt is /merged/ rather than replaced by the code/resource files in the new getdown.txt, but the digest for those old files becomes null, and so the digest fails, and then the old filename is no longer available in the website appdir, so obviously can't be downloaded.

There is at least one workaround, which is to have the new files use the same filename as the old file. This is not elegant mainly for the reason of the filename indicating a version number (but it has been checked to work).

I am still investigating other possible workarounds such as having the old filenames present in the website appdir along side the new ones (although first combination of attempts putting the old filenames as resource rather than code failed with similar error, not sure why). We don't want to have an old version of the jar present with the new version and have them both named as "code" in getdown.txt, Just In Case.