Updates

[fcastilloec]

This PR does the following:

• Upgrades dependencies to latest versions
• Promisify the whole code
• Fix tests and example

[malept]

Thanks for doing the work. Having done a similar thing in -debian, I know how tedious that can get.

I took a cursory look - it's a large PR so I'm counting on the tests to help out 😄 I only saw a couple of cosmetic things that should change.

There's inconsistent use of () around a single arrow function parameter. Personally, I'd just get rid of the parentheses.

[malept]

asarExists

[malept]

Also, I wonder if it'd be worth making some sort of electron-installer-linux-common or something, seeing as the code is similar between the now four Linux installer modules. (Maybe less so for electron-installer-snap... but that's because I only based it on my experiences maintaining these modules rather than using them as a code start point.)

[fcastilloec]

@malept The majority of the code is just replicating the work you already did on -debian and I've actually done the same thing for -windows. So the work was easier after you did it first.

Regarding the parenthesis, the "inconsistency" comes from me always using airbnb eslint rules which requires parenthesis if the function has a curly brackets body, otherwise no parenthesis. That's why it seems like there's inconsistency, but it follow that rule. Since we don't use that rule, I'll go ahead and remove all parentheses.

Regarding the common module, it might not be a bad idea. The -windows also shares a few similarities but not as much as -debian and -redhat do. It might not be worth it, but just like you, I'm only helping maintain them.