fix(client.go): fixes premature index file download

[nxtcoder17]

fixes #176
now when calling AddOrUpdateChartRepo the index file is downloaded only when the repo is not already cached in storage.

[elenz97]

Thanks @nxtcoder17 and good catch 😄 lgtm!

[nxtcoder17]

thanks @elenz97

[fischerman]

For future readers: This is a breaking change. AddOrUpdateChartRepo no longer updates the index if it exists(despite the "update" in the name). To update the index call UpdateChartRepos. It is counterintuitive that "AddOrUpdate" doesn't do the same thing as "Update" in case of an update.

@elenz97 Should this be marked in the change log as a breaking change?

[enrichman]

@fischerman Thanks for this confirmation. We had a couple of issues related to this (see epinio/epinio#2690), and checking the code I was not really sure why the Update was not really updating. I would have considered this in a different method, or changing the signature.