Fix zsh nested subcommand option completion

[ZhongRuoyu]

In zsh completion context, the words array excludes the command name, so subcommands are not matched and per-subcommand options are not suggested.

To fix that, use $words[1] instead of $words[2] when dispatching nested subcommands in generated zsh completions.

For reference, see zshcompsys's manpage ¹, specifically "the words special array and the CURRENT special parameter are modified to refer only to the normal arguments when the action is executed or evaluated":

$ man zshcompsys | col -bx | grep -F -A 13 '*::message:action'
              *::message:action
              *:::message:action
                     This describes how arguments (usually non-option
                     arguments, those not beginning with - or +) are to be
                     completed when neither of the first two forms was
                     provided.  Any number of arguments can be completed in
                     this fashion.

                     With two colons before the message, the words special
                     array and the CURRENT special parameter are modified to
                     refer only to the normal arguments when the action is
                     executed or evaluated.  With three colons before the
                     message they are modified to refer only to the normal
                     arguments covered by this description.

Also confirmed that this issue is zsh-specific. Bash and fish completions work fine.

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• AI was used to generate or assist with generating this PR.

Claude helped to locate and fix the problem.

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Footnotes

1. https://zsh.sourceforge.io/Doc/Release/Completion-System.html ↩

[Copilot]

Pull request overview

This PR fixes zsh completion dispatch for Homebrew commands with nested subcommands so per-subcommand options are suggested correctly.

Changes:

• Updates generated zsh nested subcommand completion logic to inspect $words[1].
• Regenerates affected zsh completion entries in completions/zsh/_brew.
• Adds test coverage for the corrected zsh dispatch expression.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/completions.rb	Updates nested zsh subcommand dispatch to use the correct zsh words index.
Library/Homebrew/test/completions_spec.rb	Adds an expectation covering the corrected generated zsh case statement.
completions/zsh/_brew	Applies the regenerated zsh completion output for nested subcommand completions.

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[MikeMcQuaid]

Thanks!