From ae0f63cbbb57112ae8084d0a2b639d2ec7f8793b Mon Sep 17 00:00:00 2001
From: James MacMillan <jamesiain@me.com>
Date: Tue, 24 Aug 2021 11:24:53 -0400
Subject: [PATCH] Fix for MacOS issue with diffopts=internal

Stock vim on Catalina (and, apparently, Big Sur) does not support
diffopt=internal even though the default options include internal.
Thus :set diffopt+=vertical is equivalent to
:set diffopt=internal,filler,vertical which is an error because
internal is not supported. One solution is to modify your .vimrc
as follows:

if &diff
    set diffopt-=internal
    set diffopt+=vertical
endif

The issue (and fix) is described on these websites:
https://github.com/thoughtbot/dotfiles/issues/655
https://www.micahsmith.com/blog/2019/11/fixing-vim-invalid-argument-diffopt-iwhite/
---
 vimrc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/vimrc b/vimrc
index 8f9d078848..092320919e 100644
--- a/vimrc
+++ b/vimrc
@@ -173,6 +173,10 @@ set spellfile=$HOME/.vim-spell-en.utf-8.add
 " Autocomplete with dictionary words when spell check is on
 set complete+=kspell
 
+" Fix for MacOS issue described here:
+" https://github.com/thoughtbot/dotfiles/issues/655
+set diffopt-=internal
+
 " Always use vertical diffs
 set diffopt+=vertical