nixpkgs/neovim: don't automatically strip whitespace in diffs

.config/nixpkgs/neovim/autocmd.lua

@@ -28,7 +28,14 @@ vim.api.nvim_create_autocmd('BufLeave', {
 })
 
 -- strip trailing whitespace
-vim.api.nvim_create_autocmd('BufWritePre', { command = '%s/\\s\\+$//e' })
+vim.api.nvim_create_autocmd('BufWritePre', {
+  callback = function(opts)
+    if vim.bo.filetype == 'diff' then
+      return
+    end
+    vim.cmd('%s/\\s\\+$//e')
+  end,
+})
 
 -- filetype specific options
 vim.api.nvim_create_autocmd('FileType', {