1 files changed, 29 insertions, 0 deletions
diff --git a/railties/lib/rails/app_rails_loader.rb b/railties/lib/rails/app_rails_loader.rb
new file mode 100644
index 0000000000..8937e10db3
--- /dev/null
+++ b/railties/lib/rails/app_rails_loader.rb
@@ -0,0 +1,29 @@
+require 'pathname'
+
+module Rails
+  module AppRailsLoader
+    RUBY = File.join(*RbConfig::CONFIG.values_at("bindir", "ruby_install_name")) + RbConfig::CONFIG["EXEEXT"]
+    EXECUTABLE = 'bin/rails'
+
+    def self.exec_app_rails
+      cwd = Dir.pwd
+      return unless in_rails_application_or_engine? || in_rails_application_or_engine_subdirectory?
+      exec RUBY, EXECUTABLE, *ARGV if in_rails_application_or_engine?
+      Dir.chdir("..") do
+        # Recurse in a chdir block: if the search fails we want to be sure
+        # the application is generated in the original working directory.
+        exec_app_rails unless cwd == Dir.pwd
+      end
+    rescue SystemCallError
+      # could not chdir, no problem just return
+    end
+
+    def self.in_rails_application_or_engine?
+      File.exists?(EXECUTABLE) && File.read(EXECUTABLE) =~ /(APP|ENGINE)_PATH/
+    end
+
+    def self.in_rails_application_or_engine_subdirectory?(path = Pathname.new(Dir.pwd))
+      File.exists?(File.join(path, EXECUTABLE)) || !path.root? && in_rails_application_or_engine_subdirectory?(path.parent)
+    end
+  end
+end