feat: enable file list in gemspec to work without git

.gitignore

@@ -1,3 +1,4 @@
+.DS_Store
 *.gem
 *.rbc
 .bundle
@@ -6,6 +7,7 @@ coverage
 InstalledFiles
 lib/bundler/man
 log
+*.log
 pkg
 rdoc
 spec/reports
@@ -30,6 +32,7 @@ Gemfile.lock
 
 bethtest/
 *bethtest*
+*bethtemp*
 *dogfood*
 bin/
 db/test/change_migration_strategy/pact_broker_database.sqlite3

pact_broker.gemspec

@@ -3,6 +3,28 @@ lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'pact_broker/version'
 
+def gem_files
+  if Dir.exist?(".git")
+    `git ls-files`.split($/)
+  else
+    root_path      = File.dirname(__FILE__)
+    all_files      = Dir.chdir(root_path) { Dir.glob("**/{*,.*}") }
+    all_files.reject! { |file| [".", ".."].include?(File.basename(file)) || File.directory?(file)}
+    gitignore_path = File.join(root_path, ".gitignore")
+    gitignore      = File.readlines(gitignore_path)
+    gitignore.map!    { |line| line.chomp.strip }
+    gitignore.reject! { |line| line.empty? || line =~ /^(#|!)/ }
+
+    all_files.reject do |file|
+      gitignore.any? do |ignore|
+        file.start_with?(ignore) ||
+          File.fnmatch(ignore, file, File::FNM_PATHNAME) ||
+          File.fnmatch(ignore, File.basename(file), File::FNM_PATHNAME)
+      end
+    end
+  end
+end
+
 Gem::Specification.new do |gem|
   gem.name          = "pact_broker"
   gem.version       = PactBroker::VERSION
@@ -14,7 +36,7 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version = '>= 2.2.0'
 
-  gem.files         = `git ls-files`.split($/)
+  gem.files         = gem_files
   gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]