Fix get release

[migmartri]

Changes the way we retrieve a single release name. Instead of listing all the releases and retrieving the last one, we use what Helm itself uses instead.

I have also imported a helper to extract error messages from GRPC so we can imitate what helm does without the need of having extra error handling.

// curl tiller-proxy...
{
  "code": 404,
  "message": "release: \"wordpress-miguel23\" not found"
}

Also note that this method does not require passing a namespace so changes will be made in further PRs

Refs #765

[prydonius]

Does the test need to be changed as the error message is different now?

[migmartri]

Does the test need to be changed as the error message is different now?

No, this is because the returned error by GRPC matches the previous one.

I needed to change the updateRelease code though to remove the specific error handling for 404, which I am not sure why it is needed though since the UI takes into account the code returned not the message.

[andresmgot]

Good find. I am checking the current helm code and it seems that the signature of the function is different:

https://github.com/helm/helm/blob/master/cmd/helm/get.go#L90

Is that because a newer version?

[migmartri]

Is it? I believe that it is the same. It seems to be a variadic function that accepts zero or more options

	ReleaseContent(rlsName string, opts ...ContentOption) (*rls.GetReleaseContentResponse, error)

In Helm's get CMD it passes the version but looking at the code I noticed that if you do not pass the version, the code returns the last one which is what we want https://github.com/helm/helm/blob/7cad59091a9451b2aa4f95aa882ea27e6b195f98/pkg/tiller/release_content.go#L32

[andresmgot]

👍 I didn't check the function definition