Do not escape + in Shellwords.escape

+ is not a character that requires escaping in Bourne sh.

Fixes [Bug #14429]

lib/shellwords.rb

@@ -147,7 +147,7 @@ module Shellwords
     # Treat multibyte characters as is.  It is the caller's responsibility
     # to encode the string in the right encoding for the shell
     # environment.
-    str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/, "\\\\\\1")
+    str.gsub!(/([^A-Za-z0-9_\-.,:+\/@\n])/, "\\\\\\1")
 
     # A LF cannot be escaped with a backslash because a backslash + LF
     # combo is regarded as a line continuation and simply ignored.

test/test_shellwords.rb

@@ -68,6 +68,11 @@ class TestShellwords < Test::Unit::TestCase
     assert_equal "ps -p #{$$}", joined
   end
 
+  def test_shellescape
+    assert_equal "''", shellescape('')
+    assert_equal "\\^AZaz09_\\\\-.,:/@'\n'+\\'\\\"", shellescape("^AZaz09_\\-.,:\/@\n+'\"")
+  end
+
   def test_whitespace
     empty = ''
     space = " "