commit https://github.com/vim/vim/commit/2f97912800e86a296c001832bbbf2fc425f1e533 Author: Bram Moolenaar <Bram@vim.org> Date: Thu Oct 27 17:27:44 2016 +0200 patch 8.0.0049 Problem: When a match ends in part of concealed text highlighting, it might mess up concealing by resetting prev_syntax_id. Solution: Do not reset prev_syntax_id and add a test to verify. (Christian Brabandt, closes #1092)

" Vim filetype plugin file
" Language:	Diff
" Maintainer:	Bram Moolenaar <Bram@vim.org>
" Last Change:	2005 Jul 27

" Only do this when not done yet for this buffer
if exists("b:did_ftplugin")
  finish
endif
let b:did_ftplugin = 1

let b:undo_ftplugin = "setl modeline<"

" Don't use modelines in a diff, they apply to the diffed file
setlocal nomodeline