Ban recusive asdf calls as they are inefficient and may introduce bugs.
If you find yourself needing to invoke an `asdf` command from within
asdf code, please source the appropriate file and invoke the
corresponding function.
* fix: don't invoke asdf inside asdf commands
Recursive calls have a number of disadvantages:
* Poorer performance since each invocation spawns and new process and re-executes all the code in bin/asdf
* Makes debugging more difficult
* More likely to introduce subtle bugs and the possibility for infinite loops
