Remove code duplication from sorting bookmarks

It makes the most sense to sort the global bookmarks list just before
rendering them in the NERDTree window. Since Vim's sort function is fast
and stable, and since users are very unlikely to have a number of
bookmarks that is too large, we can sort before rendering without
concern for the negligible performance penalty.

This has two benefits:
  1. Users can change their sort settings and have them take effect
     on the next render or refresh.
  2. As mentioned, code duplication is avoided.

lib/nerdtree/bookmark.vim

@@ -19,9 +19,6 @@ function! s:Bookmark.AddBookmark(name, path)
         endif
     endfor
     call add(s:Bookmark.Bookmarks(), s:Bookmark.New(a:name, a:path))
-    if g:NERDTreeBookmarksSort == 1 || g:NERDTreeBookmarksSort == 2
-        call s:Bookmark.SortBookmarksList()
-    endif
 endfunction
 
 " FUNCTION: Bookmark.Bookmarks() {{{1
@@ -104,9 +101,6 @@ function! s:Bookmark.CacheBookmarks(silent)
                 call nerdtree#echo(invalidBookmarksFound . " invalid bookmarks were read. See :help NERDTreeInvalidBookmarks for info.")
             endif
         endif
-        if g:NERDTreeBookmarksSort == 1 || g:NERDTreeBookmarksSort == 2
-            call s:Bookmark.SortBookmarksList()
-        endif
     endif
 endfunction
 

lib/nerdtree/ui.vim

@@ -313,6 +313,10 @@ function! s:UI._renderBookmarks()
         call cursor(line(".")+1, col("."))
     endif
 
+    if g:NERDTreeBookmarksSort == 1 || g:NERDTreeBookmarksSort == 2
+        call g:NERDTreeBookmark.SortBookmarksList()
+    endif
+
     for i in g:NERDTreeBookmark.Bookmarks()
         call setline(line(".")+1, i.str())
         call cursor(line(".")+1, col("."))