cli: literally don't run update-notifier in CI environment

[mislav]

This is a followup to #33 that changes the logic to literally not run update-notifier in CI environment, instead of running it and omitting the result.

Checking environment variables is a “cheap” check and, as such, should ideally come before other, potentially more expensive checks such as those that hit the filesystem or the network.

/cc @sibiraj-s @zkat

[sholladay]

update-notifier already disables itself in CI automatically:
https://github.com/yeoman/update-notifier/blob/d3718349e5c541face4a37c80feebb505de31b7c/index.js#L40-L42

[mislav]

Thank you! In that case, the check in npm should be removed entirely, instead of having it in the wrong place?

[sibiraj-s]

update-notifier already disables itself in CI automatically

update-notifier caches the data and updates itself when called the next time. this behaviour is inconstant(may be because of is-ci). somehow it still escapes. thats why i added a check here

instead of having it in the wrong place?

Yes. I could have added before initiating update notifier.

but, before any discussion check #61. I think this PR can be closed as this is already taken care of https://github.com/npm/cli/pull/61/files#diff-7e8e97e11751b950f7b30f4c8e969207R32

[mislav]

@sibiraj-s Yes, it looks like #61 supersedes this PR. This can be closed once that is merged.

[zkat]

I'm closing this one in favor of #61.