improve line ending detection + add tests

should hopefully work on Linux and Windows now

t/CMDTEST_crnl.rb

@@ -0,0 +1,75 @@
+# coding: utf-8
+
+require "selftest_utils"
+
+class CMDTEST_crnl < Cmdtest::Testcase
+
+  include SelftestUtils
+
+  def test_crnl
+    create_CMDTEST_foo [
+      'cmd "echo_crnl.rb 1:rn 2:rn" do',
+      '    comment "windows line endings"',
+      '    stdout_equal "1\n2\n"',
+      'end',
+    ]
+
+    if Cmdtest::Util.windows?
+      cmd_cmdtest do
+        stdout_equal [
+          "### windows line endings",
+        ]
+      end
+    else
+      cmd_cmdtest do
+        stdout_equal [
+          "### windows line endings",
+          "--- ERROR: Windows line ending: STDOUT",
+        ]
+        exit_nonzero
+      end
+    end
+  end
+
+  def test_nl
+    create_CMDTEST_foo [
+      'cmd "echo_crnl.rb 1:n 2:n" do',
+      '    comment "unix line endings"',
+      '    stdout_equal "1\n2\n"',
+      'end',
+    ]
+
+    if Cmdtest::Util.windows?
+      cmd_cmdtest do
+        stdout_equal [
+          "### unix line endings",
+          "--- ERROR: UNIX line ending: STDOUT",
+        ]
+        exit_nonzero
+      end
+    else
+      cmd_cmdtest do
+        stdout_equal [
+          "### unix line endings",
+        ]
+      end
+    end
+  end
+
+  def test_crnl_and_nl
+    create_CMDTEST_foo [
+      'cmd "echo_crnl.rb 1:n 2:rn" do',
+      '    comment "mixed line endings"',
+      'end',
+    ]
+
+    cmd_cmdtest do
+      stdout_equal [
+        "### mixed line endings",
+        "--- ERROR: mixed line ending: STDOUT",
+      ]
+      exit_nonzero
+    end
+  end
+
+end

t/bin/echo_crnl.rb

@@ -0,0 +1,12 @@
+#!/usr/bin/ruby
+
+STDOUT.binmode
+
+for arg in ARGV
+    arg = arg.dup
+    if arg.sub!(/:rn$/, "")
+        print arg + "\r\n"
+    elsif arg.sub!(/:n$/, "")
+        print arg + "\n"
+    end
+end