This is something I may pick up myself, but didn't have time to grab last week.

Gopherbot should only close the issue if the "Fixes #" label exists in the commit message.

That makes sense. Gopherbot shouldn't close the issue when the commit message says "Updates #nnn".

Currently, gopherbot looks for any kind of issue mention ("#nnn") simply because that's the only information that maintner exposes. In order to resolve this issue, maintner needs to be modified to expose additional information. There is an existing TODO comment in the maintner code that talks about what needs to be done to implement this:

https://github.com/golang/build/blob/6a02381872d7cdf7146a8560231970f0d3ef645b/maintner/github.go#L2502-L2506

One possible solution would be to add a new field to the GerritCL type that indicates whether or not this CL "fixes" the issue, or just updates/relates to it.

There is a maintner.GitHubIssueRef type, perhaps that information can go there. (Although doing that might require us to change the signature of the GerritCL.References method.)

See #42277 for another occurrence.

CC @golang/release, @ianlancetaylor.