text: public virtual NGit.Api.RebaseCommand SetUpstream(AnyObjectId upstream){try{this.upstreamCommit = walk.ParseCommit(upstream);this.upstreamCommitName = upstream.Name;}catch (IOException e){throw new JGitInternalException(MessageFormat.Format(JGitText.Get().couldNotReadObjectWhileParsingCommit, upstream.Name), e);}return this;}