Transcompile ..= operator to support old vims, fixes #542

ftplugin/yaml.vim

@@ -19,7 +19,7 @@ setlocal comments=:# commentstring=#\ %s expandtab
 setlocal formatoptions-=t formatoptions+=croql
 
 if !exists("g:yaml_recommended_style") || g:yaml_recommended_style != 0
-  let b:undo_ftplugin ..= " sw< sts<"
+  let b:undo_ftplugin .= " sw< sts<"
   setlocal shiftwidth=2 softtabstop=2
 endif
 

scripts/build

@@ -175,7 +175,9 @@ def copy_file(package, src, dest)
       else
         output << "if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, '#{name}') == -1\n\n"
       end
-      IO.copy_stream(input, output)
+      contents = File.read(input)
+      contents.gsub!(' ..= ', ' .= ')
+      output << contents
       output << "\nendif\n"
     end
   end