Maybe and Early milestones are no more

[Brad Fitzpatrick]

We will continue to use Go1.9Maybe & Go1.9 for this cycle. (Go1.9Early is already closed.)

Starting with Go1.10, we will not use the -Maybe or -Early milestones.

Instead of Go1.10Early, use Milestone "Go1.10" + label "early-in-cycle".

Instead of Go1.10Maybe, use Milestone "Go1.10".

"Maybe" is now the implicit default.

For "not Maybe", use the new label "release-blocker".

Why something might be a release blocker:

* a CL already exists that missed the previous cycle

* it's a regression from Go1.N to tip.

* it's a headline feature planned for Go 1.N+1.

* because you plan to work on it.

* because it's bugging a lot of people and somebody or team has committed to fixing it

* it's a performance regression

Not good reasons for something to be a release blocker:

* you really want it but don't plan to work on it and don't know who would fix it

* it's a nice-to-have minor-ish performance improvement

But there are no strict rules about what "release-blocker" means. We'll figure it out more during the Go 1.10 cycle I'm sure.

It is intentional that the label case-like-this temporarily doesn't match our existing CaseLikeThis. Details about that and this whole maybe/early business are in https://golang.org/issue/20252