Require thor 0.15.3 onwards

railties/lib/rails/generators/base.rb

@@ -20,6 +20,7 @@ class Base < Thor::Group
       include Rails::Generators::Actions
 
       add_runtime_options!
+      strict_args_position!
 
       # Returns the source root for this generator using default_source_root as default.
       def self.source_root(path=nil)

railties/railties.gemspec

@@ -22,11 +22,7 @@
   s.rdoc_options << '--exclude' << '.'
 
   s.add_dependency('rake',          '>= 0.8.7')
-
-  # The current API of the Thor gem (0.14) will remain stable at least until Thor 2.0. Because
-  # Thor is so heavily used by other gems, we will accept Thor's semver guarantee to reduce
-  # the possibility of conflicts.
-  s.add_dependency('thor',          '>= 0.14.6', '< 2.0')
+  s.add_dependency('thor',          '>= 0.15.3', '< 2.0')
   s.add_dependency('rdoc',          '~> 3.4')
   s.add_dependency('activesupport', version)
   s.add_dependency('actionpack',    version)