code: func (r *Rewriter) uncacheCommit(from []byte) ([]byte, bool) {
  	r.mu.Lock()
  	defer r.mu.Unlock()
  
  	c, ok := r.commits[hex.EncodeToString(from)]
  	return c, ok
  }
docs: // uncacheCommit returns a *git/gitobj.Commit that is cached from the given
  // *git/gitobj.Commit "from". That is to say, it returns the *git/gitobj.Commit that
  // "from" should be rewritten to and true, or nil and false if none could be
  // found.