Don't fetch tags when exact version is specified in HelmChart

[makkes]

Taking this shortcut has two benefits:

1. It allows charts to be fetched from AWS's public container registry
   at public.ecr.aws
2. It makes reconciling a HelmChart faster by skipping one or more
   potentially expensive API calls to the registry.

refs #845

[souleb]

Wouldn't it be better to do the check in downloadFromRepository before calling remote.GetChartVersion. Because remote.GetChartVersion does some expensive job in either cases, load index or fetch tags to retrieve a version. If we know we have a valid version, maybe we can save some cpu cycles here.

[makkes]

Wouldn't it be better to do the check in downloadFromRepository before calling remote.GetChartVersion. Because remote.GetChartVersion does some expensive job in either cases, load index or fetch tags to retrieve a version. If we know we have a valid version, maybe we can save some cpu cycles here.

GetChartVersion is called from two places:

1. remoteChartBuilder#downloadFromRepository
2. DependencyManager#addRemoteDependency

We'd have to change both callers to get the same behaviour. IMHO the logic to check whether to hit the remote repository or not belongs into GetChartVersion so that callers don't have to think about that. The next time someone adds a call to GetChartVersion and doesn't think about the case where the version denotes a concrete semantic version they introduce this bug again.

[souleb]

the other thing is that we rely on remote.GetChartVersion to tell us if a given version is valid(i.e. it does exit in the remote) or not before trying to download it ... We are introducing a different behavior than https helmrepo here. And the test cases have to be changed accordingly.

[makkes]

The failure on "tests / test-linux-amd64" is a flake:

panic: Failed to stop the test environment: timeout waiting for process kube-apiserver to stop

[stefanprodan]

LGTM

Thanks @makkes 🏅