handle Unicode filenames on Windows + test

by adding an argument "encoding: 'UTF-8'" to Dir.entries.
Also add minimal test.

lib/cmdtest/fssnapshot.rb

@@ -27,8 +27,16 @@ require "find"
 module Cmdtest
   class FsSnapshot
 
+    def _dir_entries(dir, &block)
+      if Cmdtest::Util.windows?
+        Dir.entries(dir, encoding: 'UTF-8', &block)
+      else
+        Dir.entries(dir, &block)
+      end
+    end
+
     def recursive_find(ignore, prefix, dir, &block)
-      for entry in Dir.entries(dir)
+      for entry in _dir_entries(dir)
         next if entry == "."
         next if entry == ".."
         path = File.join(dir, entry)

t/CMDTEST_unicode.rb

@@ -0,0 +1,25 @@
+
+require "selftest_utils"
+
+class CMDTEST_unicode < Cmdtest::Testcase
+
+  include SelftestUtils
+
+  def test_unicode
+
+    create_CMDTEST_foo [
+      "cmd 'create_unicode_file.rb' do",
+      "    created_files 'tmp-ΑΒΓ-αβγ-א-Њ-åäöÅÄÖ.txt'",
+      "end",
+    ]
+
+    cmd_cmdtest do
+      stdout_equal [
+        "### create_unicode_file.rb",
+      ]
+    end
+
+  end
+
+
+end

t/bin/create_unicode_file.rb

@@ -0,0 +1,5 @@
+#!/usr/bin/env ruby
+
+File.open('tmp-ΑΒΓ-αβγ-א-Њ-åäöÅÄÖ.txt', 'w', encoding: 'UTF-8') do |f|
+    f.puts 'this is tmp-ΑΒΓ-αβγ-א-Њ-åäöÅÄÖ.txt'
+end