Make surroundings function public

Integrate tpope#51

Author: somini

autoload/commentary.vim

@@ -1,4 +1,4 @@
-function! s:surroundings() abort
+function! commentary#surroundings() abort
   return split(get(b:, 'commentary_format', substitute(substitute(
         \ &commentstring, '\S\zs%s',' %s','') ,'%s\ze\S', '%s ', '')), '%s', 1)
 endfunction
@@ -24,7 +24,7 @@ function! commentary#go(...) abort
     let [lnum1, lnum2] = [line("'["), line("']")]
   endif
 
-  let [l, r] = s:surroundings()
+  let [l, r] = commentary#surroundings()
   let uncomment = 2
   for lnum in range(lnum1,lnum2)
     let line = matchstr(getline(lnum),'\S.*\s\@<!')
@@ -59,7 +59,7 @@ function! commentary#go(...) abort
 endfunction
 
 function! commentary#textobject(inner) abort
-  let [l, r] = s:surroundings()
+  let [l, r] = commentary#surroundings()
   let lnums = [line('.')+1, line('.')-2]
   for [index, dir, bound, line] in [[0, -1, 1, ''], [1, 1, line('$'), '']]
     while lnums[index] != bound && line ==# '' || !(stridx(line,l) || line[strlen(line)-strlen(r) : -1] != r)