Function remove_credentials_keep_history 

fn remove_credentials_keep_history(
    dir: &Path,
    history: Option<&str>,
) -> Result<Option<PathBuf>>

Remove dir, keeping its history child when that child is a real, non-empty directory. Returns the kept path, or None when the whole tree was removed.

A history child that is a link (a symlink, or a Windows junction — the isolated-auth redirect to the always-global history, see identity_auth_dirs::link_history_if_isolated) does not hold the history itself, so the whole tree goes; remove_dir_all removes the link without following it. An empty history child is nothing to keep.

Keeps removing the other entries after one fails, so one locked file doesn’t leave the rest of the credential behind, then reports the first failure.