I work on a bilingual website built with Hugo, and to build it i run the hugo command twice, each time with a different config file. The problem is that i have two directories under public that have the same static files (each has its own copy). This is unnecessary and redundant. I wonder if there is a way to let theme share the same static files (css, js, images).
Sure. Just use the default static dir setting, or the same for both. The static files will be copied twice, but as they are the same … only one of each end up in public.
Setting staticdir to different values and putting the static files in those directories.
I guess it is also possible to have two totally separate Hugo sites, or build to multiple output folders (public1, public2), but I suggest you read the core part of the documentation, try to understand it.