Their names are not perfect, so let's keep them as internal functions,
until we figure out how/if we want to expose this.
This reverts 0445126c2 (Undunder __fish_is_nth_token, 2021-06-29) (but I
did it without "git revert").
Closes#8008
We keep __fish_is_nth_token for compatibility and edit the
implementations of __fish_is_nth_token, __fish_is_first_token and
__fish_is_token_n to use fish_is_nth_token
Only the first non-switch parameter to python must be a .py file, but
everything thereafter is "just another argument". This enables file
completions for 2nd+ arguments.
The issue here was that the `python` completion did a version check on
the `python` binary, so it would complete python2 stuff if system
python was py2, even if the user tried to complete `python3`.
This isn't beautiful, but it's more resilient than e.g. doing magic
with `commandline`.
Fixes#3840.
