list.sh: only show headings when there are items to show

[ZhongRuoyu]

If there are no formulae or casks to show, then don't show the "Formulae" or "Casks" headings. This used to be the case when there was only the Ruby implementation, and continues to be the case when the Ruby implementation is used ¹, so we should maintain the consistency.

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Footnotes

1. https://github.com/Homebrew/brew/blob/4a95077682ae5f342cf60ff181ebbcfb03d49117/Library/Homebrew/cmd/list.rb#L162-L170 ↩

[Copilot]

Pull request overview

Updates the fast-path brew list shell implementation (list.sh) to better match the Ruby implementation by only printing section headings when there are items to display.

Changes:

• Move the “Formulae” heading to only print when the formula list output is non-empty.
• Move the “Casks” heading to only print when the cask list output is non-empty.

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[MikeMcQuaid]

Makes sense!