Refactor gemspec

- remove unnecessary files
- remove reference to not included executables
- add bug tracker URL

Author: mblumtritt

mutex_m.gemspec

@@ -1,28 +1,27 @@
 begin
-  require_relative "lib/mutex_m"
+  require_relative 'lib/mutex_m'
 rescue LoadError
   # for Ruby core repository
-  require_relative "mutex_m"
+  require_relative 'mutex_m'
 end
 
 Gem::Specification.new do |spec|
-  spec.name          = "mutex_m"
-  spec.version       = Mutex_m::VERSION
-  spec.authors       = ["Keiju ISHITSUKA"]
-  spec.email         = ["[email protected]"]
+  spec.name = 'mutex_m'
+  spec.version = Mutex_m::VERSION
+  spec.authors = ['Keiju ISHITSUKA']
+  spec.email = ['[email protected]']
 
-  spec.summary       = %q{Mixin to extend objects to be handled like a Mutex.}
-  spec.description   = %q{Mixin to extend objects to be handled like a Mutex.}
-  spec.homepage      = "https://github.com/ruby/mutex_m"
-  spec.licenses      = ["Ruby", "BSD-2-Clause"]
+  spec.summary = 'Mixin to extend objects to be handled like a Mutex.'
+  spec.description = spec.summary
+  spec.homepage = 'https://github.com/ruby/mutex_m'
+  spec.metadata['source_code_uri'] = spec.homepage
+  spec.metadata['bug_tracker_uri'] = "#{spec.homepage}/issues"
+  spec.licenses = %w[Ruby BSD-2-Clause]
 
-  spec.files         = ["Gemfile", "LICENSE.txt", "README.md", "Rakefile", "lib/mutex_m.rb", "mutex_m.gemspec"]
-  spec.bindir        = "exe"
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
-  spec.require_paths = ["lib"]
+  spec.files = %w[LICENSE.txt README.md lib/mutex_m.rb]
   spec.required_ruby_version = '>= 2.5'
 
-  spec.add_development_dependency "bundler"
-  spec.add_development_dependency "rake"
-  spec.add_development_dependency "test-unit"
+  spec.add_development_dependency 'bundler'
+  spec.add_development_dependency 'rake'
+  spec.add_development_dependency 'test-unit'
 end