Comment 8 for bug 1870314

Thank you for the review. I'm fixing the config file location typo in the next upload.

Ubuntu's package installation ensures that modified local configuration files are not overwritten without consent.
Having an old file in /etc/... triggers the following question which is better than silently ignoring the newly shipped file, like in upstream's postinst:

Configuration file '/etc/default/instance_configs.cfg'
 ==> File on system created by you or by a script.
 ==> File also in package provided by package maintainer.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.
*** instance_configs.cfg (Y/I/N/O/D/Z) [default=N] ?

For installing config files conditionally there is ucf, but it is overkill here.