Book excerpt: There's a change in the air. High-profile projects such as the Linux Kernel, Mozilla, Gnome, and Ruby on Rails are now using Distributed Version Control Systems (DVCS) instead of the old stand-bys of CVS or Subversion. Git is a modern, fast, DVCS. But understanding how it fits into your development can be a daunting task without an introduction to the new concepts. Whether you're just starting out as a professional programmer or are an old hand, this book will get you started using Git in this new distributed world.