Function ignore_files::discover_file

pub async fn discover_file(
    files: &mut Vec<IgnoreFile>,
    errors: &mut Vec<Error>,
    applies_in: Option<PathBuf>,
    applies_to: Option<ProjectType>,
    path: PathBuf
) -> bool

Utility function to handle looking for an ignore file and adding it to a list if found.

This is mostly an internal function, but it is exposed for other filterers to use.