Introduce `Rails.gem_version`

This method return `Gem::Version.new(Rails.version)`, suggesting a more
reliable way to perform version comparison.

Example:

    Rails.version #=> "4.1.2"
    Rails.gem_version #=> #<Gem::Version "4.1.2">

    Rails.version > "4.1.10" #=> false
    Rails.gem_version > Gem::Version.new("4.1.10") #=> true
    Gem::Requirement.new("~> 4.1.2") =~ Rails.gem_version #=> true

This was originally introduced as `.version` by @charliesome in #8501
but got reverted in #10002 since it was not backward compatible.

Also, updating template for `rake update_versions`.

1 files changed, 12 insertions, 0 deletions

diff --git a/railties/test/version_test.rb b/railties/test/version_test.rb
new file mode 100644
index 0000000000..f270d8f0c9
--- /dev/null
+++ b/railties/test/version_test.rb
@@ -0,0 +1,12 @@
+require 'abstract_unit'
+
+class VersionTest < ActiveSupport::TestCase
+  def test_rails_version_returns_a_string
+    assert Rails.version.is_a? String
+  end
+
+  def test_rails_gem_version_returns_a_correct_gem_version_object
+    assert Rails.gem_version.is_a? Gem::Version
+    assert_equal Rails.version, Rails.gem_version.to_s
+  end
+end