This is the source for the 1st edition of the Pro Git book. The second edition has since been released and is what will be maintained and published going forward. Please suggest any changes to that version instead.
You can find the new edition at:
https://github.com/progit/progit2
If you're looking for the original README content, it can be found in the README.original.md file.