Allow passing the chart repo to helm template

[aackerman]

Resolves #277

[mumoshu]

Wow, I've never realized helm had this option and I'm entirely unsure when this is supposed to be used, but I learned that it works like:

helm template --repo https://charts.helm.sh/stable envoy

Anyway, we'd better have this to make it consistent with helm template.

LGTM. Thanks a lot for your contribution @aackerman!

[aackerman]

@mumoshu awesome, thanks for getting this merged. This is important for remote repos that aren't already local.

[mumoshu]

@aackerman Thanks for the info! So, this just frees you from being required to run helm repo add beforehand, right?

[aackerman]

@mumoshu yep that's definitely what I'm using it for

[mumoshu]

@aackerman Got it. Thanks for clarifying ☺️

[dex4er]

Wow, it simplify my deployment scripts too. I had to add special exception in my scripts and do extra and unecessary helm repo add FOO BAR --force-update 1>&2 && helm repo update >/dev/null whenever I run helm diff.

Thanks!