The patchsetSha is one of the things passed in to the `fetch()`
interface, and Buildkite's API (now?) supports filtering by the commit
hash in addition.
With this combination, we should not accidentally display builds for
the wrong patch set.
Change-Id: I6bb26dd7387f2dd00291990cadd38629ecda999b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5702
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>