CodePush.sync() API method

[lostintangent]

This provides a simplified and opinionated one-line experience to CodePush-ifying an app. The CodePush.sync() method allows automating the act of checking for an update, downloading it and then subsequently applying it, all while also supporting ignoring previously failed updates, respecting mandatory updates and displaying a standard user confirmation dialog when updates are available.

The method takes an optional options object that can be used to customize the strings used when displaying the user dialog, as well as the rollback timeout.

It returns a Promise that will be resolved with a SyncStatus code, that indicates why the sync succeeded:

0 - No update was available, so the running app is up to do
1 - The app had an optional update, but the end-user chose to ignore it
2 - The app had an optional or mandatory update and the user accepted it

If a failure occurs at any point during the sync, the returned Promise will be rejected with the error reason.

I'll update the docs in a subsequent PR, but I just wanted to get this change out since the respective Cordova change is in review.

[geof90]

LGTM!

[dtivel]

failedApply?

[dtivel]

LGTM

[richardhuaaa]

Hey I don't think a failure in the apply promise is being handled here - would it be better to do:

 return localPackage.apply(syncOptions.rollbackTimeout); }) .catch(reject) .done(); 

[richardhuaaa]

LGTM!