Use default deployer in 'skaffold apply'

[nkubala]

EDIT: merge after: #5791

#5543 added support for skaffold apply to send rendered manifests to a cluster, but didn't plumb through the creation of the default deployer all the way. this change makes sure that always happen with the apply command is issued.

[codecov]

Codecov Report

Merging #5776 (9dc311e) into master (8efc9ef) will decrease coverage by 0.00%.
The diff coverage is 82.89%.

@@            Coverage Diff             @@
##           master    #5776      +/-   ##
==========================================
- Coverage   71.00%   71.00%   -0.01%     
==========================================
  Files         438      439       +1     
  Lines       16497    16495       -2     
==========================================
- Hits        11714    11712       -2     
  Misses       3921     3921              
  Partials      862      862              

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/apply.go	25.00% <0.00%> (ø)
cmd/skaffold/app/cmd/delete.go	57.14% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	56.52% <0.00%> (ø)
cmd/skaffold/app/cmd/diagnose.go	64.51% <ø> (ø)
cmd/skaffold/app/cmd/filter.go	25.58% <0.00%> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.48% <0.00%> (ø)
cmd/skaffold/app/cmd/generate_pipeline.go	61.53% <0.00%> (ø)
cmd/skaffold/app/cmd/render.go	40.74% <0.00%> (ø)
cmd/skaffold/app/cmd/runner.go	58.49% <0.00%> (ø)
cmd/skaffold/app/cmd/test.go	46.66% <0.00%> (ø)
... and 131 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fb9c352...9dc311e. Read the comment docs.

[briandealwis]

So we're using apply = true to implicitly test getDefaultDeployer(). I think it would be better to test getDefaultDeployer() explicitly, and add some more cases like Kustomize flags and conflicts.

[nkubala]

there is actually another set of test cases below this one that tests getDefaultDeployer() explicitly - the main thing I changed here is to embed the if runCtx.Opts.Apply check in the call to getDeployer() which sends us through to getDefaultDeployer(), which I thought cleaned up the code in NewForConfig() a bit.

the addition of the apply boolean to this set of tests just tests the branching logic that ensures if we're in skaffold apply, we get a default deployer - the other tests make sure that all the other cases (e.g. Kustomize flags, unresolvable config, etc.) are working as intended.

[nkubala]

CI is failing because of an issue with skaffold diagnose, which is fixed by #5791

[MarlonGamez]

lgtm 👍🏼