Adds and commits all files, printing the output of each command. The noteworthy thing here is the second command, which has to be executed as an array rather than a String.

git-commit.groovy

#!/usr/bin/env groovy

def process = "git add .".execute()
println process.text

// This next one has to be done as an array because of the space in the -am argument.
process = ["git", "commit", "-am 'First commit'"].execute()
println process.text