Staged rollout support for vscode extensions

[hyangah]

Originally opened as a feature request in VS Code repo (microsoft/vscode#170631)

VS Code auto-updates extensions as soon as the new versions become available if the user does not opt out of the auto-update feature. As an extension publisher (golang.go), we are often worried about the scale of damage one bad release can result in.

It would be nice if extension publishers can have some control over the rollout speed.

e.g. push to ~10% for day1, ~40% for day3, release fully on day4.... We may want to roll out emergency update or critical security patch more aggressively.

Thorough testing before release, long baking time using prerelease/insider versions, ability to unpublish problematic versions https://github.com/microsoft/vsmarketplace/issues/235 all can help mitigating the issue, but they do not completely eliminate large scale failures.

Staged rollout support is nothing new in other mobile, desktop app stores. VS Code itself recognized the same kind of problem in https://github.com/microsoft/vscode/issues/15602. I don't know exactly how VS Code addressed this issue eventually but I see staged rollout was also mentioned in https://github.com/microsoft/vscode/issues/15602#issuecomment-261122661.

Extensions are important part of VS Code ecosystem. Often the quality/stability of extensions is interpreted as that of VS Code. Staged rollout will help extension publishers improving their extensions while limiting the potential risk that may affect a large number of VS Code users.

[tooltitude-support]

Would be really great to have it!