Download and modify file from Git Repository using Ruby Grit over SSH

How can I download a file (or clone the repo) from a secure Git Repo (e.g. SSH on GitHub), then commit changes back to the开发者_JAVA百科 repo using Ruby Grit? Thanks!

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Grit gives you object oriented read/write access to Git repositories via Ruby.
-- http://grit.rubyforge.org/

Grit is just for interacting with a local repo, it doesn't manage remote ops (clone/push/pull/fetch) for you.