Setting the argument name with `dest` is ignored

[mathieulongtin]

Summary

You used to be able to override the argument name with dest, but that doesn't work anymore.

This was useful to allow things like --json without overriding the json module, for example.

To Reproduce

Python script:

import argh

@argh.arg("-l", dest="list_files")
def somefunc(list_files=False):
  pass

Command line input/output:

$ my-script.py ...
argh.assembling.ArgumentNameMappingError: somefunc: argument -l does not fit function signature: -l/--list-files

Expected behavior

The old behavior where if dest is supplied, it overrides any guesses as to the destination argument.

Environment

• OS: Ubuntu
• Python version: 3.10
• Argh version: 0.31.2

Additional context

Add any other context about the problem here.

[neithere]

Thanks, confirming, scheduled the next bugfix release.

[neithere]

Related, not necessarily a replacement: #222.