Add a string that marks inserted comments (tpope#87)

doc/commentary.txt

@@ -29,6 +29,19 @@ gcu
                                                 *:Commentary*
 :[range]Commentary      Comment or uncomment [range] lines
 
+                                                *g:commentary_marker*
+g:commentary_marker     A string that marks comments inserted by commentary.
+                        This marker is inserted immediately after the comment
+                        string. Useful if commentary is only used to disable
+                        code (rather than inserting explanatory comments).
+
+                        For example, >
+                            let g:commentary_marker = '~'
+<                        will comment >
+                            f();
+<                        into >
+                            //~ f();
+
 The |User| CommentaryPost autocommand fires after a successful operation and
 can be used for advanced customization.
 

plugin/commentary.vim

@@ -8,9 +8,15 @@ if exists("g:loaded_commentary") || v:version < 700
 endif
 let g:loaded_commentary = 1
 
+if !exists("g:commentary_marker")
+  let g:commentary_marker = ''
+endif
+
 function! commentary#surroundings() abort
+  " Ensure whitespace around %s and postfix comment leader with ~ to make auto
+  " commented code easier to find.
   return split(get(b:, 'commentary_format', substitute(substitute(substitute(
-        \ &commentstring, '^$', '%s', ''), '\S\zs%s',' %s', '') ,'%s\ze\S', '%s ', '')), '%s', 1)
+        \ &commentstring, '^$', '%s', ''), '\S\zs%s', g:commentary_marker.' %s', '') ,'%s\ze\S', '%s ', '')), '%s', 1)
 endfunction
 
 function! s:strip_white_space(l,r,line) abort