Function workdir_or_cwd 

pub fn workdir_or_cwd(
    store: &BufferStoreHandle,
    scopes: &RepoScopes,
    active: BufferId,
) -> PathBuf

active_workdir with the working directory as the fall-back — the form the operation helpers want, since they need a directory to run git in and “not in a repository” is git’s error to report, not ours.