git-xargs is a command-line tool (CLI) for making updates across
multiple GitHub repositories with a single command. You give
git-xargs:

 - a script or a command to run
 - a list of repos

and git-xargs will:

 - clone each repo
 - run your specified script or command against it
 - commit any changes
 - open pull requests
 - provide a detailed report of everything that happened

Git-xargs leverages goroutines to perform the repo-updating work in
parallel, so it is very fast.
