From d44f088834081ee404db4459fdcfba82d14ef157 Mon Sep 17 00:00:00 2001
From: Jonas Strittmatter <40792180+smjonas@users.noreply.github.com>
Date: Mon, 17 Oct 2022 08:18:57 +0200
Subject: [PATCH] =?UTF-8?q?vim-patch:9.0.0771:=20cannot=20always=20tell=20?=
 =?UTF-8?q?the=20difference=20beween=20tex=20and=20=E2=80=A6=20(#20687)?=
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vim-patch:9.0.0771: cannot always tell the difference beween tex and rexx files

Problem:    Cannot always tell the difference beween tex and rexx files.
Solution:   Recognize tex by a leading backslash. (Martin Tournoij,
            closes vim/vim#11380)
https://github.com/vim/vim/commit/bd053f894b0d7652928201faa68c53d1ce2acdc5
---
 runtime/autoload/dist/ft.vim        | 2 +-
 runtime/lua/vim/filetype/detect.lua | 2 +-
 src/nvim/testdir/test_filetype.vim  | 5 +++++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 7333e5a7e7..17abc90637 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -145,7 +145,7 @@ func dist#ft#FTcls()
     return
   endif
 
-  if getline(1) =~ '^%'
+  if getline(1) =~ '^\v%(\%|\\)'
     setf tex
   elseif getline(1)[0] == '#' && getline(1) =~ 'rexx'
     setf rexx
diff --git a/runtime/lua/vim/filetype/detect.lua b/runtime/lua/vim/filetype/detect.lua
index 7fc7f1b7ca..23fa1c5068 100644
--- a/runtime/lua/vim/filetype/detect.lua
+++ b/runtime/lua/vim/filetype/detect.lua
@@ -181,7 +181,7 @@ function M.cls(bufnr)
     return vim.g.filetype_cls
   end
   local line = getlines(bufnr, 1)
-  if line:find('^%%') then
+  if line:find('^[%%\\]') then
     return 'tex'
   elseif line:find('^#') and line:lower():find('rexx') then
     return 'rexx'
diff --git a/src/nvim/testdir/test_filetype.vim b/src/nvim/testdir/test_filetype.vim
index 7669b3d82a..1ceab2a67a 100644
--- a/src/nvim/testdir/test_filetype.vim
+++ b/src/nvim/testdir/test_filetype.vim
@@ -1768,6 +1768,11 @@ func Test_cls_file()
   call assert_equal('tex', &filetype)
   bwipe!
 
+  call writefile(['\NeedsTeXFormat{LaTeX2e}'], 'Xfile.cls')
+  split Xfile.cls
+  call assert_equal('tex', &filetype)
+  bwipe!
+
   " Rexx
 
   call writefile(['# rexx'], 'Xfile.cls')