Disregard Ruby patch level for modern rubies

It's no longer meaningful since Ruby 2.0.0.

Now the resolution error when the Ruby version does not match is better
because it does not include a weird 4th segment.

bundler/lib/bundler/definition.rb

@@ -746,17 +746,8 @@ def metadata_dependencies
 
     def ruby_version_requirements(ruby_version)
       return [] unless ruby_version
-      if ruby_version.patchlevel
-        [ruby_version.to_gem_version_with_patchlevel]
-      else
-        ruby_version.versions.map do |version|
-          requirement = Gem::Requirement.new(version)
-          if requirement.exact?
-            "~> #{version}.0"
-          else
-            requirement
-          end
-        end
+      ruby_version.versions.map do |version|
+        Gem::Requirement.new(version)
       end
     end
 

bundler/lib/bundler/ruby_version.rb

@@ -110,14 +110,6 @@ def self.system
       @ruby_version ||= RubyVersion.new(ruby_version, patchlevel, ruby_engine, ruby_engine_version)
     end
 
-    def to_gem_version_with_patchlevel
-      @gem_version_with_patch ||= begin
-        Gem::Version.create("#{@gem_version}.#{@patchlevel}")
-      rescue ArgumentError
-        @gem_version
-      end
-    end
-
     def exact?
       return @exact if defined?(@exact)
       @exact = versions.all? {|v| Gem::Requirement.create(v).exact? }

bundler/lib/bundler/rubygems_ext.rb

@@ -67,6 +67,23 @@ def gem_dir
       full_gem_path
     end
 
+    unless const_defined?(:LATEST_RUBY_WITHOUT_PATCH_VERSIONS)
+      LATEST_RUBY_WITHOUT_PATCH_VERSIONS = Gem::Version.new("2.1")
+
+      alias_method :rg_required_ruby_version=, :required_ruby_version=
+      def required_ruby_version=(req)
+        self.rg_required_ruby_version = req
+
+        @required_ruby_version.requirements.map! do |op, v|
+          if v >= LATEST_RUBY_WITHOUT_PATCH_VERSIONS && v.release.segments.size == 4
+            [op == "~>" ? "=" : op, Gem::Version.new(v.segments.tap {|s| s.delete_at(3) }.join("."))]
+          else
+            [op, v]
+          end
+        end
+      end
+    end
+
     def groups
       @groups ||= []
     end

bundler/lib/bundler/source/metadata.rb

@@ -5,7 +5,7 @@ class Source
     class Metadata < Source
       def specs
         @specs ||= Index.build do |idx|
-          idx << Gem::Specification.new("Ruby\0", RubyVersion.system.to_gem_version_with_patchlevel)
+          idx << Gem::Specification.new("Ruby\0", RubyVersion.system.gem_version)
           idx << Gem::Specification.new("RubyGems\0", Gem::VERSION) do |s|
             s.required_rubygems_version = Gem::Requirement.default
           end

bundler/spec/bundler/ruby_version_spec.rb

@@ -498,31 +498,5 @@
         end
       end
     end
-
-    describe "#to_gem_version_with_patchlevel" do
-      shared_examples_for "the patchlevel is omitted" do
-        it "does not include a patch level" do
-          expect(subject.to_gem_version_with_patchlevel.to_s).to eq(version)
-        end
-      end
-
-      context "with nil patch number" do
-        let(:patchlevel) { nil }
-
-        it_behaves_like "the patchlevel is omitted"
-      end
-
-      context "with negative patch number" do
-        let(:patchlevel) { -1 }
-
-        it_behaves_like "the patchlevel is omitted"
-      end
-
-      context "with a valid patch number" do
-        it "uses the specified patchlevel as patchlevel" do
-          expect(subject.to_gem_version_with_patchlevel.to_s).to eq("#{version}.#{patchlevel}")
-        end
-      end
-    end
   end
 end

bundler/spec/install/gems/resolving_spec.rb

@@ -301,7 +301,7 @@
       end
 
       let(:ruby_requirement) { %("#{RUBY_VERSION}") }
-      let(:error_message_requirement) { "~> #{RUBY_VERSION}.0" }
+      let(:error_message_requirement) { "= #{RUBY_VERSION}" }
 
       shared_examples_for "ruby version conflicts" do
         it "raises an error during resolution" do

lib/rubygems.rb

@@ -864,9 +864,7 @@ def self.ruby_version
     return @ruby_version if defined? @ruby_version
     version = RUBY_VERSION.dup
 
-    if defined?(RUBY_PATCHLEVEL) && RUBY_PATCHLEVEL != -1
-      version << ".#{RUBY_PATCHLEVEL}"
-    elsif defined?(RUBY_DESCRIPTION)
+    if defined?(RUBY_DESCRIPTION)
       if RUBY_ENGINE == "ruby"
         desc = RUBY_DESCRIPTION[/\Aruby #{Regexp.quote(RUBY_VERSION)}([^ ]+) /, 1]
       else

lib/rubygems/specification.rb

@@ -657,6 +657,8 @@ def rdoc_options
     @rdoc_options ||= []
   end
 
+  LATEST_RUBY_WITHOUT_PATCH_VERSIONS = Gem::Version.new("2.1")
+
   ##
   # The version of Ruby required by this gem.  The ruby version can be
   # specified to the patch-level:
@@ -683,6 +685,14 @@ def rdoc_options
 
   def required_ruby_version=(req)
     @required_ruby_version = Gem::Requirement.create req
+
+    @required_ruby_version.requirements.map! do |op, v|
+      if v >= LATEST_RUBY_WITHOUT_PATCH_VERSIONS && v.release.segments.size == 4
+        [op == "~>" ? "=" : op, Gem::Version.new(v.segments.tap {|s| s.delete_at(3) }.join("."))]
+      else
+        [op, v]
+      end
+    end
   end
 
   ##

test/rubygems/test_gem.rb

@@ -1114,14 +1114,6 @@ def test_self_ruby_version_with_patchlevel_less_ancient_rubies
     util_restore_RUBY_VERSION
   end
 
-  def test_self_ruby_version_with_release
-    util_set_RUBY_VERSION '1.8.6', 287
-
-    assert_equal Gem::Version.new('1.8.6.287'), Gem.ruby_version
-  ensure
-    util_restore_RUBY_VERSION
-  end
-
   def test_self_ruby_version_with_non_mri_implementations
     util_set_RUBY_VERSION '2.5.0', 0, 60928, 'jruby 9.2.0.0 (2.5.0) 2018-05-24 81156a8 OpenJDK 64-Bit Server VM 25.171-b11 on 1.8.0_171-8u171-b11-0ubuntu0.16.04.1-b11 [linux-x86_64]'