Include available versions for all the packs in the index

[Kami]

This pull request updates generate index script so we now also include all the available versions for each pack in the index.json file.

Implementation

This implementation utilizes Github API to retrieve all the available tags for a particular pack repo.

TODO

• Handle Github authentication so we get a higher rate limit

[Kami]

I updated the script so we use Github credentials we generate for each pack repo.

I first thought we might have API rate limiting issues, but we use different Github credentials for each pack deployment so we should be fine.

The whole process is still a bit inefficient since I followed the existing approach which means we rebuild the whole index on each pack deployment. I will file this under "feature improvement / optimization" :)

I also confirmed it's working at StackStorm-Exchange/stackstorm-slack#52 (https://circleci.com/gh/StackStorm-Exchange/stackstorm-slack/255, StackStorm-Exchange/index@16d6c1d).

[arm4b]

tags in context of Exchange index and as a property of the pack could have a little bit generic meaning.
If the goal here to list all available released versions, maybe versions or releases would be a better naming?

Additionally, the PR doesn't make it clear which functionality relies on a list of available pack versions in the exchange index.

[Kami]

@armab I agree, versions / available_versions is a better name for that attribute (and it's also consistent with the existing version attribute).

At this point no functionality relies on this attribute yet, but there are various use cases for it (e.g. right now listing available pack versions in StackStorm CLI depends on git, etc.).

[Kami]

@armab Here we go - 8b86314 (StackStorm-Exchange/index@1a165bd).

[arm4b]

LGTM

Resolved.