info: avoid Formula/Cask objects for counts

[MikeMcQuaid]

• use Tab runtime_dependencies hashes and rack directory existence instead of instantiating Formula or Cask objects for dependency/dependent counts
• replace rack.subdirs.max_by mtime stat calls with rack.subdirs.last since dep names rarely change across versions
• skip JSON parsing in count_installed_dependents when the formula name doesn't appear in the raw receipt file
• skip dependent counting entirely for non-TTY output

mike book # hyperfine --prepare "git checkout a93c2bbf023fbfb1f52324eb8652c5be941ee2e0" "OLD=1 brew info ruby" --prepare "git checkout main" "CURRENT=1 brew info ruby" --prepare "git checkout info-perf-avoid-formula-objects" "NEW=1 brew info ruby"
Benchmark 1: OLD=1 brew info ruby
  Time (mean ± σ):     974.4 ms ± 131.9 ms    [User: 545.4 ms, System: 227.4 ms]
  Range (min … max):   864.0 ms … 1336.1 ms    10 runs
 
Benchmark 2: CURRENT=1 brew info ruby
  Time (mean ± σ):      1.345 s ±  0.138 s    [User: 0.890 s, System: 0.264 s]
  Range (min … max):    1.235 s …  1.722 s    10 runs
  
Benchmark 3: NEW=1 brew info ruby
  Time (mean ± σ):     885.6 ms ±  29.3 ms    [User: 517.8 ms, System: 213.8 ms]
  Range (min … max):   845.3 ms … 929.1 ms    10 runs

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Used Claude Code with manual review and testing.

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[Copilot]

Pull request overview

Optimizes brew info dependency/dependent counting by using installed keg Tab data and filesystem checks instead of instantiating Formula/Cask objects, reducing runtime overhead in interactive output.

Changes:

• Add a receipt/tab-based dependent counting helper and use keg tab runtime_dependencies for recursive runtime counts.
• Update cask dependency “installed?” checks to use Cellar/Caskroom directory existence.
• Adjust specs to create minimal Cellar/Caskroom state to exercise the new code paths.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
Library/Homebrew/cmd/info.rb	Switches dependency/dependent counting to use Tab/Cellar inspection and adds a new counting helper.
Library/Homebrew/cask/info.rb	Avoids loading Formula/Cask objects when determining whether dependencies are installed.
Library/Homebrew/test/cmd/info_spec.rb	Updates formula info spec to build keg/tab fixtures in the Cellar.
Library/Homebrew/test/cask/info_spec.rb	Updates cask info spec to create Caskroom directories for “installed” detection.

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