Property files for localization requires to be encoded in ISO-8859-1.
It results difficulties in reviewing localizing pull requires such as https://github.com/jenkinsci/maven-plugin/pull/86.
It would be nice if property files in source directories can be written in UTF-8 letters.

There are two approaches:

1. Encode property files when compiling.
   • maven-resources-plugin copies files in the resources directory into the target directory. It doesn't provide a feature to encode property files.
   • Though native2ascii-maven-plugin encodes property files, it is provided only as beta for long time.
     • This might mean encoding property files in compilation time isn't a standard approach.
   • maven-antrun-plugin can run native2ascii (But it feels strange approach to me).
   • This approach would cause problems when testing plugins with "mvn hpi:run".
     • As property files aren't compiled and read from source directories directly at that time.
2. Make libraries reading property files accept UTF-8 letters.
   • localizer: https://github.com/kohsuke/localizer
   • stapler (stapler-jelly): https://github.com/stapler/stapler/

Actually, I'm not sure this is a good idea.
I created this ticket and will create pull requests to request comments about this idea.