feat: add _comp_xfunc

[akinomyoga]

Resolve #732

• 2c7ca22 add _comp_xfunc
• 2b4bb19 use _comp_xfunc instead of _xfunc
• fc0b4b8 add _comp_deprecate_func for backward-compatibility names

The function _comp_deprecate_func is introduced to later automatically detect the use of old function names for #542. To implement #542, some codes can be added in the automatically generated function body in _comp_deprecate_func.

[scop]

Looks good to me, thanks!

Left a bunch of rather trivial comments, pre-approved with those addressed, but feel free to bounce back if you think they deserve more discussion or I missed something.

[akinomyoga]

I have rebased and squashed the changes. For the additional changes compared to the previous version, I have made comments of the commit hashes in each conversation.

[akinomyoga]

Now I noticed that there can be a case where an external completion calls any function that is not marked xfunc by us through _xfunc. Maybe we need to still allow such cases for backward compatibility as 35fbf57, or do we recommend continuing to use the deprecated _xfunc in such a case? Hmm, what do you think?

[scop]

35fbf57 makes sense to me. With that, couldn't we just _comp_deprecate_func _xfunc _comp_xfunc considering that our separate completion files don't have any functions that would not start with an underscore?

[akinomyoga]

Thank you!

• ce9b010 I have supplemented 35fbf57 with an appropriate update of the description
• ffb59f4 I have moved _comp_deprecate_func to the beginning of the file to use it for functions defined in the main bash_completion, and applied it to _comp_xfunc
• f8a6a09 I have added input checks to _comp_deprecate_func

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I have rebased and squashed.

[scop]

Nice! I took the liberty to fix the completions/ssh conflict my push last night caused in your repo, force-pushed there and merged here.

[akinomyoga]

Thanks!