code: func (r *Rewriter) uncacheEntry(from *gitobj.TreeEntry) *gitobj.TreeEntry {
  	r.mu.Lock()
  	defer r.mu.Unlock()
  
  	return r.entries[r.entryKey(from)]
  }
docs: // uncacheEntry returns a *TreeEntry that is cached from the given *TreeEntry
  // "from". That is to say, it returns the *TreeEntry that "from" should be
  // rewritten to, or nil if none could be found.