When trying to use the pub global activate via the flutter packages pub pass-through, I see an error:

Error: No pubspec.yaml file found.
This command should be run from the root of your Flutter project.
Do not run this command from the root of your git clone of Flutter.

However, the pub global activate does not require a pubspec; it can be run from anywhere.

I believe the PackagesPassthroughCommand class in commands/packages.dart should be updated tp not require a pubspec.