Bring in latest `pub`

[kevmoo]

The last sync of pub was on Aug 8 - dart-lang/pub@9f00679

We've had a number of commits since – dart-lang/pub@SDK-2.1.0-dev.1.0...master – and we've added a changelog validaor, logout command, support for global activation via a custom pub URL, etc.

It'd be nice to roll this in, no?

CC @mit-mit @sigurdm

[mit-mit]

Too late for 2.2; that is going out today. But, yes we should bring this over.

[sigurdm]

I've created https://dart-review.googlesource.com/c/sdk/+/94380

[kevmoo]

Before we close out this issue, can we do another sync? ...to grab dart-lang/pub#2014

[sigurdm]

https://dart-review.googlesource.com/c/sdk/+/94744

[vsmenon]

Is this still open?

[kevmoo]

Fixed in 895bc90