Fix OptionParser#program_name not to strip suffix unexpectedly

Author: nobu

lib/optparse.rb

@@ -1294,7 +1294,15 @@ def banner
   # to $0.
   #
   def program_name
-    @program_name || File.basename($0, '.*')
+    @program_name || strip_ext(File.basename($0))
+  end
+
+  private def strip_ext(name)  # :nodoc:
+    exts = /#{
+      require "rbconfig"
+      Regexp.union(RbConfig::CONFIG["EXECUTABLE_EXTS"])
+    }\z/o
+    name.sub(exts, "")
   end
 
   # for experimental cascading :-)

test/optparse/test_optparse.rb

@@ -216,4 +216,16 @@ def stdout.tty?; true; end
       end
     end
   end
+
+  def test_program_name
+    program = $0
+    $0 = "rdbg3.5"
+    assert_equal "rdbg3.5", OptionParser.new.program_name
+    RbConfig::CONFIG["EXECUTABLE_EXTS"].split(" ") do |ext|
+      $0 = "rdbg3.5" + ext
+      assert_equal "rdbg3.5", OptionParser.new.program_name
+    end
+  ensure
+    $0 = program
+  end
 end