Add useHelm3 flag

[SimonAlling]

It doesn't work yet, but will be needed later on (see #1309).

As pointed out by @absoludity: "I think it's fine to land with the useHelm2/3 switch available but clearly document that it's not yet working, as long as it isn't changing current behaviour […]."

[SimonAlling]

I don't understand why the CI failed. Do you, @andresmgot and @absoludity?

Downloading mongodb from repo https://kubernetes-charts.storage.googleapis.com
Deleting outdated charts
Error: release kubeapps-ci failed: Secret in version "v1" cannot be handled as a Secret: v1.Secret.ObjectMeta: v1.ObjectMeta.TypeMeta: Kind: Data: decode base64: illegal base64 data at input byte 4328, error found in #10 byte of ...| useHelm3"},"kind":"|..., bigger context ...|5EIFJTQSBQUklWQVRFIEtFWS0tLS0t # matches useHelm3"},"kind":"Secret","metadata":{"labels":{"app":"kub|...

[absoludity]

I don't understand why the CI failed. Do you, @andresmgot and @absoludity?

Downloading mongodb from repo https://kubernetes-charts.storage.googleapis.com
Deleting outdated charts
Error: release kubeapps-ci failed: Secret in version "v1" cannot be handled as a Secret: v1.Secret.ObjectMeta: v1.ObjectMeta.TypeMeta: Kind: Data: decode base64: illegal base64 data at input byte 4328, error found in #10 byte of ...| useHelm3"},"kind":"|..., bigger context ...|5EIFJTQSBQUklWQVRFIEtFWS0tLS0t # matches useHelm3"},"kind":"Secret","metadata":{"labels":{"app":"kub|...

Yeah - the issue is that you can't have comments in yaml scalar values, but if you template your branch (and in particular, include the tiller tls which ci does), you'll see:

(useHelm3-flag) ~/dev/kubeapps$ helm template ./chart/kubeapps/ --set tillerProxy.tls.key=./script/test-certs/helm.key.pem --set tillerProxy.tls.cert=./script/test-certs/helm.cert.pem  | grep useHelm3
    Li9zY3JpcHQvdGVzdC1jZXJ0cy9oZWxtLmtleS5wZW0= # matches useHelm3
    heritage: Tiller # matches useHelm3
    namespace: default # matches useHelm3
    release: release-name # matches useHelm3
            secretName: release-name-kubeapps-internal-tiller-proxy # matches useHelm3

The main issue there is the secret value (first line), where the comment is included as part of the secret value. I'd remove the matches useHelm3 as we really don't want those in the yaml output. If you want to keep them to help devs, then perhaps use a template comment instead? ie.:

--- a/chart/kubeapps/templates/tiller-proxy-secret.yaml
+++ b/chart/kubeapps/templates/tiller-proxy-secret.yaml
@@ -23,4 +23,4 @@ data:
   tls.key: |-
 {{ .Values.tillerProxy.tls.key | b64enc | indent 4 }}
 {{- end -}}
-{{- end }} # matches useHelm3
+{{- end }}{{/* matches useHelm3 */}}

Otherwise, +1 from me :)

[absoludity]

lgtm (with fix in comment above)

[SimonAlling]

Wow, that's some interesting interaction between YAML and Go templates right there, @absoludity! I fully agree that the comments shouldn't be in the output. The recently pushed commit seems to have done the trick, but since I had forgotten to merge master into the PR branch first, I did that just now instead.