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Re: We should add a "git gc --auto" after "git clone" due to commit graph

On Wed, Oct 03, 2018 at 02:59:34PM -0400, Derrick Stolee wrote:

> > They don't help yet, and there's no good reason to enable bitmaps for
> > clients. I have a few patches that use bitmaps for things like
> > ahead/behind and --contains checks, but the utility of those may be
> > lessened quite a bit by Stolee's commit-graph work.  And if it isn't,
> > I'm mildly in favor of replacing the existing .bitmap format with
> > something better integrated with commit-graphs (which would give us an
> > opportunity to clean up some of the rough edges).
> If the commit-graph doesn't improve enough on those applications, then we
> could consider adding a commit-to-commit reachability bitmap inside the
> commit-graph. ;)

That unfortunately wouldn't be enough for us to ditch the existing
.bitmap files, since we need full object reachability for some cases
(including packing). And commit-to-commit reachability is a trivial
subset of that. I'm not sure if it would be better to just leave
.bitmaps in place as a server-side thing, and grow a new thing for
commit-to-commit reachability (since it would presumably be easier).

I'm still excited about the prospect of a bloom filter for paths which
each commit touches. I think that's the next big frontier in getting
things like "git log -- path" to a reasonable run-time.