grid plugin: Initial branch from query parameter?

[zware]

Hi,

I believe that at some point, the grid view allowed including branch=... in the URL to set the branch shown, but this appears to no longer work (e.g. https://buildbot.python.org/#/grid?branch=3.13 still defaults to (all)). If it never did and I'm just imagining past behavior, please consider this a feature request rather than a bug report :)

Background: python/buildmaster-config#327; we would like to include a link to PR-specific results in our messages, and grid seems like our best option for that without resorting to a custom plugin. If there are better options that I'm unaware of, we're all ears!

[p12tic]

This should be possible to include into Buildbot, probably not even that complex.