fix: correctly set namespace when checking for an existing helm release via skaffold deploy

[mrparkers]

Fixes: #3838

Description

When using skaffold deploy with helm, skaffold was not honoring the --namespace command-line flag when checking if a helm release already exists. You can reproduce this error using the code within the examples/helm-deployment folder:

Before this PR:

cd examples/helm-deployment
kubectl create ns skaffold-test
skaffold build -q | skaffold deploy --namespace skaffold-test --build-artifacts - # results in a successful deployment
skaffold build -q | skaffold deploy --namespace skaffold-test --build-artifacts - # results in the error "cannot re-use a name that is still in use"

After this PR:

cd examples/helm-deployment
kubectl create ns skaffold-test
skaffold build -q | skaffold deploy --namespace skaffold-test --build-artifacts - # results in a successful deployment
skaffold build -q | skaffold deploy --namespace skaffold-test --build-artifacts - # results in a successful helm upgrade

[mrparkers]

cc @clement-buchart

[mrparkers]

side note: please correct me if I'm wrong, but it looked like a lot of the assertions for the existing unit tests around the helm deploy code were incorrect - most of them were asserting that the --namespace flag was not used in the first helm get, but was used in the following helm upgrade. this didn't make sense to me, I think that we should be expecting that the --namespace flag is used in both cases or in neither case.

I went ahead and fixed these tests and added a few more that used a namespaced skaffold context to assert that the --namespace flag is being used when the skaffold context contains a namespace, even if the helm release does not contain a namespace.

please let me know if I misunderstood something here and if I have to revert it back to the way it was.

[codecov]

Codecov Report

Merging #3914 into master will increase coverage by 0.02%.
The diff coverage is 91.66%.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/helm.go	78.80% <91.66%> (+1.03%)	⬆️
pkg/skaffold/server/server.go	58.57% <0.00%> (ø)

[dgageot]

Awesome! Thanks a lot @mrparkers