Add ability to write completions to the file

[arcan1s]

It might be useful to write file directly instead of forwarding output to it, e.g. if files are generated automatically in pipeline (via tox or whatever is used) and distributed together with an application. No append option supported.

This commit also updates docs for cases when it is possible to write file directly and no sudo required to write there

[casperdcl]

Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.91%. Comparing base (1d7a36b) to head (6cac14c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #192      +/-   ##
==========================================
+ Coverage   88.88%   88.91%   +0.03%     
==========================================
  Files           3        3              
  Lines         360      361       +1     
==========================================
+ Hits          320      321       +1     
  Misses         40       40              

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[casperdcl]

Apparently this will be deprecated python/cpython#58032 - might prefer a different implementation.

[arcan1s]

oof, tbh I don't think in context of this tools we would even actually be affected by the mentioned issues, but nevertheless (because of deprecation) I've replaced logic to (optional) Path argument and handle it accordingly (i.e. if empty, then emit sys.stdout and file descriptor otherwise). I've also added few tests to cover new code

Please, let me know if you would like to see another solution here