thunderbird-android/cli/html-cleaner-cli/README.md

Usage: html-cleaner [OPTIONS] INPUT [OUTPUT]

  A tool that modifies HTML to only keep allowed elements and attributes the
  same way that K-9 Mail does.

Options:
  -h, --help  Show this message and exit

Arguments:
  INPUT   HTML input file (needs to be UTF-8 encoded)
  OUTPUT  Output file

You can run this tool using the html-cleaner script in the root directory of this repository. It will compile the application and then run it using the given arguments. This allows you to make modifications to the HTML cleaning code and test the changes right away.