Last updated February 28, 2013.
Every project features a tab with Git instructions on the Version control tab (as shown below). On this tab either as a regular user or project maintainer you can find instructions for accessing the git repo for a project.
For project maintainers
The Git URL provided to you uses ssh to communicate with the drupal.org servers. You can only push changes to your project's repository using ssh.
N.B. Git submodules, while allowed by the repositories on drupal.org, will not be included in releases.
You can also switch to the view available to non maintainers (e.g. if you want to see the right instructions to provide other people). That view is shown in the section below.
For users who are not committers
The tab is also available, but shows a http URL for cloning the project Git repo. You cannot push useing this URL.