This is all about setting up GIT repository to behave in such a way that all developers can push their changes and can pull others changes from central shared repository, ultimately they are going to clone the repository into their local location and each user's "working copy" will itself be a fully-fledged Git repository but to make the code changes centralized they have to push and pull to the central repository that can be on a remote server. e.g. http://source.example.com , we will call this server as source.
I am glad to be part of a team who deployed Drupal as an Intranet platform for a Fortune 20 telecom company. This is the first time that Drupal was used on an open surce LAMP stack to create a corporate Intranet for over 90,000 employees. The project was a complete rewrite of the existing intranet that had been in operation for over half a decade. It was accomplished in less than 12 months from conception to full deployment, ramping up from just a one member team to a 17 person group with only 5 full time developers