Re: [PATCH 1/1] fetch: add fetch.writeCommitGraph config setting

> > You're right that we could isolate the new write to the refs we
> > just received. We could use the more cumbersome write_commit_graph()
> > method with a list of commit oids as starting points. I'm happy to
> > make that change if we see a lot of value there.
> 
> Well, that is not the kind of information reuse I am talking about.
> 
> I was wondering if "index-pack" has enough information in-core after
> it receives and processes the incoming pack data, scanned each and
> every object in it, in order to write out the commit graph _without_
> having to do a lot of duplicate computation and enumeration of the
> objects done in the current commit-graph.c::write_commit_graph(), so
> that it can learn a "--write-commit-graph" option that performs much
> better than running "git fetch && git commit-graph write".
> 
> Perhaps that would require too much refactoring of both index-pack
> and commit-graph code and infeasible in short to medium term and
> that is why I said "for longer term, it feels a bit unfortunate".