All serious web development agencies use Git in their work. Using Git has become a must for every more or less large project.
What is it? It is a distributed version-control system that helps track changes that were made in a code.
Why? Well, here are some arguments:
The DesignRussia agency is a fan of Git. We use it for nearly all our projects. Thanks to Git, our clients can also monitor a development process in real time by receiving Git notifications to their emails and check the code of each new commit by themselves.