List all the rake tasks

rake -T

will only show you documented tasks. In order to list all the tasks, you need to append the -A option.

rake -AT

Display the tasks (matching optional PATTERN) with descriptions, then exit. -AT combination displays all of the tasks contained no description.
Please note that passing -TA options won't work, however, you can pass them separately.

rake -TA   # doesn't work 
rake -T -A # works

All the above commands could be called via rails instead of rake inside a rails project.

rails -AT