github-linguist/linguist ? reverse-engineered prompt

Build me a Ruby tool that can look at a Git repo or a single file and tell me what language it is, plus show a percentage breakdown of the whole repository by language. It should ignore binary files, vendored code, and generated files when figuring out the results, and it should be able to explain how it made each decision when I ask for a more detailed view. I want a command line app that works with no options for a quick summary, and also supports showing file by file breakdowns, JSON output, and analyzing an older branch or tag if I point it at a different revision. It should respect repo overrides so I can force or change how certain files are classified. Please make it usable as a library too, so another Ruby app can load it and ask for a repo’s main language and language stats. If you need to look up current docs for any Ruby or Git bindings, go ahead and do that.