Showing or displaying the available tasks inside a fabric fabfile is one of those things that almost everyone wants to do at some point and usually works out you can just request a task you know will not exist (usually found through a typo). However there is a way to list them built into fabric itself.
The below are all methods which can be used to display the currently defined tasks.
fab -l fab -list fab taskthatdoesnotexist
Try any of the above where a fabfile is located and be presented with a list of all the available tasks.