Replace git ls-files with Dir globs in gemspec

[ogajduse]

Summary

This PR replaces git ls-files with explicit Dir globs in the gemspec, following Ruby packaging best practices.

Fixes #125

Changes

Modified clamp.gemspec line 23:

# Before
s.files = `git ls-files`.split("\n")

# After
s.files = Dir["lib/**/*", "examples/**/*", "spec/**/*", "*.md", "LICENSE", "Rakefile", "Gemfile", "#{s.name}.gemspec"]

Why This Change?

Using git ls-files in gemspecs is considered bad practice by the Ruby community:

Problem 1: Git dependency breaks builds

• ❌ Package builds: Fails in Debian/RPM clean environments without git
• ❌ Docker: Breaks in minimal production images
• ❌ Git archives: Fails with GitHub release tarballs (no .git/ directory)

Problem 2: Includes unnecessary files

Current gem includes development files that bloat the package:

• .github/workflows/ci.yml
• .rubocop.yml, .rspec, .autotest, .editorconfig
• CODEOWNERS, Guardfile

Benefits

✅ No git dependency - Works in all build environments
✅ Explicit file list - Clear, maintainable, intentional
✅ Cleaner gems - Production-ready files only
✅ Simpler downstream packaging - No manual exclusion lists needed
✅ No breaking changes - All necessary files still included

Verification

Tested locally by building and unpacking the gem:

gem build clamp.gemspec
gem unpack clamp-1.4.0.gem
ls -la clamp-1.4.0/  # ✓ No .github/, no dotfiles

Files included (clean):

• lib/ (source code)
• examples/ (examples)
• spec/ (tests)
• CHANGES.md, README.md (documentation)
• LICENSE, Rakefile, Gemfile, clamp.gemspec

Files excluded (as intended):

• .github/, .rubocop.yml, .rspec, .autotest, etc.
• CODEOWNERS, Guardfile

Community Recommendations

This approach is recommended by:

• Ruby Packaging Style Guide
• RuboCop Packaging cops
• Bundler #2287: "git ls-files is bad practice"
• ruby-progressbar #54: "Don't rely on git ls-files"

Real-world Impact

This issue was discovered during RPM packaging for the Foreman project, where the Travis CI → GitHub Actions migration broke builds because the spec file couldn't keep up with upstream changes.

This change eliminates that maintenance burden for all downstream packagers.