How to tell git to ignore all further edit to a single file without removing it from the repo

Question

Use this:

git update-index --skip-worktree path/file.cfg

And to restore:

git update-index --no-skip-worktree path/file.cfg

Lastly, if you want to list files that are marked with skip-worktree:

git ls-files -v | grep ^S | awk '{print $2}'

To simplify, you can make an alias for that in your $HOME/.gitconfig:

[alias]
    ls-ignored-changes = !git ls-files -v | grep ^S | awk '{print $2}'

Then you can type just git ls-ignored-changes. It even works with auto-completion if you have the git-completion in place (for bash, tcsh, zsh).