Vert guarantees a single file/directory when you extract something with it. If there are more than 1 file in the archive it will nest them in a directory. I have no plans to add any flags or anything to make it extract without nesting either.
So it detects if there's a single folder inside the zip containing all the files or all the files directly inside the zip?
Yes. It also has l (lowercase L) subcommand which lists the contents of the archives to the terminal (stdout).
UPDATE: Implemented VERT_USE_EXTERNAL_TOOLS environment variable. See #Configuration.
I had passed the filter parameter as "data", which should help prevent most issues with it but yes I agree that it would've been better to use external tools to do the heavy-lifting. I avoided them to make the program cross-platform and easier to setup (you currently can just run a simple pip command to install it). I may introduce them as optional backends later with a warning on the default ones but for now I'm postponing it.
If anybody is curious, it's a real preprocessor for Python called PyGyat.