D9573: branchmap: update rev-branch-cache automatically [POC]

[Joerg Sonnenberger]

On Sun, Dec 13, 2020 at 06:50:45PM +0000, joerg.sonnenberger (Joerg Sonnenberger) wrote:
> REVISION SUMMARY
>   Introduce an optional callback in changelog.add and provide it in
>   localrepo to update the revbranchcache for all new changes. Ignore the
>   now redundant bundle part.

The general goal here is to provide a stable base for property caches
like the topic map. I also think it can allow making the whole
branchmap update less expensive. The downside is that we need to
actually look at the changeset, which we tried to avoid in the past.

Joerg