Function context 

pub fn context<F: Fs>(
    db: &GraphDb<F>,
    repo: Option<&Path>,
    target: &str,
) -> ContextReport

Everything known about target.

repo is the working tree the source is quoted from; without one the GitSync marker’s repo is used, and a file that cannot be read there simply has no source. Everything else is read from the graph, so the answer is byte-identical for the same store and the same working tree.