Standard completion of current option

[Roy-Orbison]

Make options complete in a manner more consistent with other shell programs.

Closes #5845.

This relies on array_key_last() which may need to be polyfilled if it isn't already.

[Roy-Orbison]

@swissspidy What tests would you need for this change? You can verify it with the following commands:

(COMP_LINE='wp search-replace --report'; wp cli completions --line="$COMP_LINE" --point=${#COMP_LINE})

produces

--report 
--report-changed-only

preserving the current word. Repeating the word, e.g.

(COMP_LINE='wp search-replace --report --report'; wp cli completions --line="$COMP_LINE" --point=${#COMP_LINE})

produces only

--report-changed-only

which demonstrates that this change preserves the existing "don't complete options that have already been typed" behaviour. The $assoc_args could be named bit better if this is its only purpose.

[Roy-Orbison]

array_key_last() appears to be polyfilled by symfony/polyfill-php73 and used in symfony/console on the dev repo, but I don't see it in the stable phar. Would you prefer another dependency, or a single line of more verbose code?

[swissspidy]

We do have some tests in cli-bash-completion.feature that could be amended for this change, and a couple are already failing right now. I'm not really familiar with the completion script to provide exact guidance, I'll defer that to the others.

As for array_key_last, can this use something like key( end( $words ) ) instead? Then we wouldn't have to fiddle with the dependencies

[Roy-Orbison]

I updated the tests to accommodate the change to the repeated option behaviour, but I don't think there are any commands in this package with an option that's a prefix of another. A command package would have to be included during testing to perform that check.

[schlessera]

Thanks, @Roy-Orbison !