[Feature Idea] Parallel Execution

[albertalef]

Problem: Independent commands run sequentially; can't leverage multiple cores.

Solution: Add parallel execution block.

sh do
  # Run commands in parallel, wait for all to complete
  results = parallel do
    grep("error", "log1.txt")
    grep("error", "log2.txt")
    grep("error", "log3.txt")
  end

  results.each { |r| puts r.stdout }
end

# With concurrency limit
sh do
  parallel(max: 4) do
    files.each { |f| gzip(f) }
  end
end

# Fail-fast mode (stop all on first error)
sh do
  parallel(fail_fast: true) do
    test_suite_1
    test_suite_2
    test_suite_3
  end
end

Implementation:

• Create RubyShell::Parallel executor using threads or Process.fork
• Collect results from all parallel commands
• Add options for concurrency limit, fail-fast behavior