From 7e0e503fb431a90b61ff66b7b6cbd7a8d49a4e58 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Sun, 3 May 2020 23:44:09 +1200
Subject: Flesh out new undoskip.vim plugin a lot

---
 vim/plugin/undoskip.vim | 50 ++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/vim/plugin/undoskip.vim b/vim/plugin/undoskip.vim
index d3ebcca2..80609433 100644
--- a/vim/plugin/undoskip.vim
+++ b/vim/plugin/undoskip.vim
@@ -1,10 +1,46 @@
-" Don't save undo history for temporary or secure files
+"
+" undoskip.vim: Don't save undo history for temporary or secure files.
+"
+" Author: Tom Ryder <tom@sanctum.geek.nz>
+" License: Same as Vim itself
+"
+if exists('loaded_undoskip') || &compatible || v:version < 700
+  finish
+endif
+let loaded_undoskip = 1
+
+" Set the paths to test; can be changed by the user
+let undoskip#patterns = ['^/dev/shm/.', '^/tmp/.', '^/var/tmp/.']
+
+" Internal function returns a local value for 'undofile'
+function s:CheckUndoSkip() abort
+
+  " If this isn't a normal buffer, don't save undo data
+  if &buftype !=# ''
+    return 0
+  endif
+
+  " Get the path from the buffer name; if that path matches any of the
+  " patterns, don't save undo data
+  let path = bufname('%')
+  for pattern in g:undoskip#patterns
+    if path =~# pattern
+      return 0
+    endif
+  endfor
+
+  " Otherwise, we'll use whatever the global setting is
+  return &g:undofile
+
+endfunction
+
+" Command interface into the private function's value, does the actual set
+command -nargs=0 CheckUndoSkip
+      \ let &l:undofile = s:CheckUndoSkip()
+
+" Check the path on every buffer rename, create, or read
 augroup undoskip
   autocmd!
-  autocmd BufAdd,BufNewFile,BufRead
-        \ *
-        \ setlocal undofile<
-  autocmd BufAdd,BufNewFile,BufRead
-        \ /dev/shm/*,/tmp/*,/var/tmp/*
-        \ setlocal noundofile
+  autocmd BufAdd,BufNewFile,BufRead *
+        \ CheckUndoSkip
 augroup END
-- 
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