In what sense is it lost? I see a "TryBots are happy." message with a "TryBot-Result +1" vote at https://go-review.googlesource.com/c/go/+/167978#message-c36076efcbed3a38e87c5f6d4de374821854b7f5.

Are you referring to the top-level view of the CL not showing any votes?

@dmitshur, yes, he's referring to the overall score on the CL. This is due to copyMinScore ... we have our Code-Review=+2 copied, but not +1 votes. See https://gerrit-review.googlesource.com/Documentation/config-labels.html#label_copyMinScore

But yes, the coordinator should & could check that a commit differs only in commit message and manually re-copy the vote without re-trying it. (But we shouldn't do the same with rebases, of course.)

@mvdan @bradfitz How about the case when the commit only update comment lines?

It's great if we can retain the result in this case, too.

@Gnouc, that's not 100% guaranteed to result in the same results. (gofmt checks, allhelp.go staleness checks, etc)

@heschik ran into this today in https://go-review.googlesource.com/c/go/+/174740/3#message-2ed0cb78dcc91bc5f91e7c424595f08bc212e465.

To avoid running into this again until this issue is resolved, don't update commit message right after starting a trybot run.

Edit: Perhaps it was different in that it wasn't just the label that was lost, but the trybot result message as well.

I'm planning to dedicate some time to this next week.

From looking into this, I understand this should be a matter of updating the copyCondition of the "Run-TryBot" and "TryBot-Result" labels to be NO_CODE_CHANGE (rather than its current NO_CHANGE):

NO_CODE_CHANGE:

Matches when a new patch set is uploaded that has the same parent tree as the previous patch set and the same code diff (including context lines) as the previous patch set. This means only the commit message may be different; the change hasn’t even been rebased. Also matches if the commit message is not different, which means this includes matching patch sets that have NO_CHANGE as the change kind.

Will mail a CL.

Implemented the change in https://go-review.googlesource.com/c/All-Projects/+/418075/. Editing only the commit message (but otherwise same parent and same tree) now keeps the Run-TryBot and TryBot-Result votes. So it's now possible to make commit message adjustments before submission without needing to rerun trybots.

(Coordinator still tracks the precise commit which it tested, so if the commit message is edited while a TryBot run is underway, the Run-TryBot vote will persist and coordinator will prefer to start again on the latest patch set. Teaching coordinator to detect equal tree/parent and persist the build is more involved and I'll consider out of scope of this issue. It's still better than before in that it always restarts without a need to manually reapply the Run-TryBot vote.)