GitHub integration
If you're using deploy tracking, and deploying from a github repository, then you'll see the git revision listed when you view the deploys for a project. The revision links straight to the exact tree that was deployed.

Also, when you view an error that happened while a deploy was active, you'll see that some of the lines of the backtrace are links. These point straight at the exact line in the backtrace on GitHub:

GitHub integration depends on deploy tracking, and so is only available on paid accounts.
But I'm not using Capistrano!
Airbrake Notifier adds a hook into Capistrano, so that deploying
automatically notifies Airbrake of your deploy. If you're not using
Capistrano, you can notify Airbrake of a deploy by using a rake
task that's provided by the airbrake gem, like so:
rake airbrake:deploy TO=#{rails_env} REVISION=#{current_revision} REPO=#{repository} USER=#{local_user}
A specific example of this for a git repository could look like:
rake airbrake:deploy TO=$RAILS_ENV REVISION=`git rev-parse HEAD` USER=`whoami` REPO=`git remote -v show | cut -f 2`