fix: properly wire deploy.kubectl.defaultNamespace field to be set in SKAFFOLD_NAMESPACES

[aaron-prindle]

fixes #7995

manually tested using repro skaffold.yaml

apiVersion: skaffold/v4beta1
kind: Config
build:
  artifacts:
  - image: skaffold-example
manifests:
  rawYaml:
  - k8s-pod.yaml
deploy:
  kubectl:
    defaultNamespace: test-ns
    hooks:
      before:
        - host:
            command: [ "sh", "-c", "echo $SKAFFOLD_NAMESPACES" ]
      after:
        - host:
           command: [ "sh", "-c", "echo $SKAFFOLD_NAMESPACES" ]

Before fix:

aprindle@aprindle-ssd ~/testNS $ skaffold dev --default-repo=gcr.io/aprindle-test-cluster
Listing files to watch...
 - skaffold-example
Generating tags...
 - skaffold-example -> gcr.io/aprindle-test-cluster/skaffold-example:latest
Some taggers failed. Rerun with -vdebug for errors.
Checking cache...
 - skaffold-example: Found Remotely
Tags used in deployment:
 - skaffold-example -> gcr.io/aprindle-test-cluster/skaffold-example:latest@sha256:9e84858382575e6f47a5a1162466a378e7ec8a79859095145794ca4df66a1582
Starting deploy...
Starting pre-deploy hooks...

Completed pre-deploy hooks
 - error: the namespace from the provided object "default" does not match the namespace "test-ns". You must pass '--namespace=default' to perform this operation.
Cleaning up...
 - error: the namespace from the provided object "default" does not match the namespace "test-ns". You must pass '--namespace=default' to perform this operation.
WARN[0002] deployer cleanup:kubectl delete: exit status 1  subtask=-1 task=DevLoop
kubectl apply: exit status 1

After fix:

aprindle@aprindle-ssd ~/testNS $ skaffold dev --default-repo=gcr.io/aprindle-test-cluster
Listing files to watch...
 - skaffold-example
Generating tags...
 - skaffold-example -> gcr.io/aprindle-test-cluster/skaffold-example:latest
Some taggers failed. Rerun with -vdebug for errors.
Checking cache...
 - skaffold-example: Found Remotely
Tags used in deployment:
 - skaffold-example -> gcr.io/aprindle-test-cluster/skaffold-example:latest@sha256:9e84858382575e6f47a5a1162466a378e7ec8a79859095145794ca4df66a1582
Starting deploy...
Starting pre-deploy hooks...
test-ns
Completed pre-deploy hooks
 - pod/getting-started created
Waiting for deployments to stabilize...
 - pods is ready.
Deployments stabilized in 3.213 seconds
Starting post-deploy hooks...
test-ns
Completed post-deploy hooks
Waiting for deployments to stabilize...
Deployments stabilized in 34.480275ms
Press Ctrl+C to exit
Watching for changes...
[getting-started] Hello world!

Note: before the fix SKAFFOLD_NAMESPACES is empty in pre/post hook AND deploy fails. Fixed now

[codecov]

Codecov Report

Merging #8129 (1173f9d) into main (290280e) will decrease coverage by 4.19%.
The diff coverage is 53.26%.

@@            Coverage Diff             @@
##             main    #8129      +/-   ##
==========================================
- Coverage   70.48%   66.28%   -4.20%     
==========================================
  Files         515      599      +84     
  Lines       23150    29355    +6205     
==========================================
+ Hits        16317    19459    +3142     
- Misses       5776     8447    +2671     
- Partials     1057     1449     +392     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/completion.go	13.04% <0.00%> (-1.25%)	⬇️
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/test.go	44.44% <0.00%> (ø)
cmd/skaffold/app/exitcode.go	100.00% <ø> (+6.66%)	⬆️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/render.go	35.48% <18.18%> (-5.90%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/run.go	64.28% <33.33%> (-9.63%)	⬇️
... and 394 more

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