Add conventional gem building infra

.gitignore

@@ -1,2 +1,8 @@
-.yardoc
-doc
+/.bundle/
+/.yardoc
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/

Rakefile

@@ -1,8 +1,10 @@
+require "bundler/gem_tasks"
 require "rake/testtask"
 
-Rake::TestTask.new do |t|
+Rake::TestTask.new(:test) do |t|
   t.libs << "test"
+  t.libs << "lib"
+  t.test_files = FileList["test/**/*_test.rb"]
 end
 
-desc "Run tests"
 task default: :test

personnummer.gemspec

@@ -1,20 +1,27 @@
-$:.push File.expand_path("../lib", __FILE__)
-require "swedish_pin/version"
+require_relative "lib/swedish_pin/version"
 
 Gem::Specification.new do |s|
   s.name = "swedish-pin"
   s.version = SwedishPIN::VERSION
-  s.date = "2020-08-09"
+  s.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
+
+  s.license = "MIT"
   s.summary = "Work with Swedish PINs (Personnummer)"
   s.description = "Parse, validate, and generate Swedish Personal Identity Numbers (PINs / Personnummer)"
+  s.homepage = "https://github.com/Mange/swedish-pin-ruby"
+
   s.authors = ["Magnus Bergmark", "Jack Millard", "Fredrik Forsmo"]
   s.email = ["me@mange.dev", "millard64@hotmail.co.uk", "fredrik.forsmo@gmail.com"]
-  s.files = `git ls-files`.split("\n")
-  s.test_files = `git ls-files -- {test,spec,features}/*`.split("\n")
-  s.executables = `git ls-files -- bin/*`.split("\n").map { |f| File.basename(f) }
+
+  # Specify which files should be added to the gem when it is released.
+  # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
+  s.files = Dir.chdir(File.expand_path("..", __FILE__)) do
+    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
+  end
+  s.bindir = "exe"
+  s.executables = s.files.grep(%r{^exe/}) { |f| File.basename(f) }
   s.require_paths = ["lib"]
-  s.homepage = "https://github.com/Mange/swedish-pin-ruby"
-  s.license = "MIT"
+
   s.add_development_dependency "rake"
   s.add_development_dependency "minitest"
   s.add_development_dependency "standard"