x/build/cmd/coordinator: subrepo trybots testing against security branch

[bradfitz]

Seen on a trybot run:

https://go-review.googlesource.com/c/tools/+/156078

Build is still in progress...
This change failed on linux-amd64 (Go 1.10-security.x):
See https://storage.googleapis.com/go-build-log/25ca8f49/linux-amd64_578e3eba.log

I suspect there's a bug in the fixes for #17626, or old assumptions that no longer apply now that we have a security branch.

Maybe just filter out the security branch before we find the last N=2 releases?

Or delete the security branch altogether?

[dmitshur]

Or delete the security branch altogether?

We did delete them in the canonical repository (i.e., https://go.googlesource.com/go/+refs). However, it continues to show up in the GitHub mirror repository (even after a manual deletion) due to a bug in gitmirror, see #23099 (comment).

I suspect we'll want to fix this with a quick trybot-specific workaround first, because the underlying issues in gitmirror (and/or in maintner) may take significantly longer to investigate and fix (and can be done independently afterwards).

[dmitshur]

This is worse than I originally understood, because trybots are not just testing the security release-branches in addition to normal release-branches, but rather only the security release-branches.

It's not too bad since the security release branches are pretty representative of Go 1.11 and Go 1.10, which is the goal of #17626, but we should still fix it so that the latest release-branches get tested. I'll start looking into this soon.

[gopherbot]

Change https://golang.org/cl/157443 mentions this issue: maintner/maintnerd/maintapi: ignore unexpected release branches