Can't stage lines when using custom textconv diff driver

[staticssleever668]

Describe the bug
Can't stage lines when using custom textconv diff driver. Either garbage gets applied or an error appears.

error: patch failed: cp866.txt:1
error: cp866.txt: patch does not apply

To Reproduce
Steps to reproduce the behavior:

1. Set up a custom textconv driver in your gitconfig

[diff "my-diff-cp866"]
  textconv = "iconv -f cp866"

2. cd "$(mktemp -d)" && echo "*.txt text diff=my-diff-cp866" >> .gitattributes && git init && echo -e "КОТ1\\nКОТ2" > utf8.txt && echo -e "КОТ1\\nКОТ2" | iconv -t cp866 > cp866.txt
3. lazygit and try to stage lines in cp866.txt and utf8.txt
   First time stages garbage. Second time gives an error.

Expected behavior
A line is staged.

Screenshots

Version info:
commit=, build date=, build source=nix, version=0.45.0, os=linux, arch=amd64, git version=2.47.0

Additional context
Perhaps wherever lazygit invokes git-diff with --no-ext-diff it should also use --no-textconv.