Re: Distinguishing FF vs non-FF updates in the reflog?

[Jeff King <peff@peff.net>]

On Thu, Mar 18, 2021 at 04:31:24PM -0600, Martin Fick wrote:

> On Thursday, March 18, 2021 9:58:56 AM MDT Han-Wen Nienhuys wrote:
> > The bitmaps are generated by GC, and you can't GC all the time. 
> 
> I believe that I recently saw an effort to make this incremental, perhaps 
> related to the geometric repacking series? If that were the case, you could gc 
> much more often cheaply. Perhaps it could be something done on every upload at 
> some point the way that reflog effectively does on every update?

That geometric repacking work is leading up to having a bitmap for a
multi-pack-index. Which will make them _cheaper_, but still not
especially cheap (because we've reordered the objects corresponding to
each bit, and also because our writing process still does a lot of
O(nr_commits) work).

In the very long run, I think the way out would be to stop using pack or
midx ordering as the basis of the bitmap, and instead have a stable
object ordering that can be appended to. That would allow true
incremental generation of the bitmaps (leaving old ones in place, and
just adding a new ones to represent new commits). But that's such a big
departure from the status quo that having a midx bitmap seemed like a
more attainable middle ground in the meantime.

-Peff