kustomize dependencies include environment files (#3720)

[nicknovitski]

Fixes #3720.

Description

ConfigMapGenerators and SecretGenerators can have env or envs fields, with paths to "environment files", with a format like this:

foo=bar
baz=qux

Each line in the file creates a new key-value pair in the generated ConfigMap or Secret. Thus, changes to the contents of those files should trigger redeploys.

User facing changes

Before

While running skaffold dev or debug, changes to the environment files would not trigger a redeploy.

After

They do.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes unit tests
• Mentions any output changes.
• Adds documentation as needed: user docs, YAML reference, CLI reference.
• Adds integration tests if needed.

Reviewer Notes

• The code flow looks good.
• Unit test added.
• User facing changes look good.

Release Notes

- kustomize deployer correctly watches for changes to files listed in the `env` or `envs` keys of `configMapGenerators` and `SecretGenerators`

[nicknovitski]

If I remember right, a maintainer has to approve the running of the kokoro tests.

[codecov]

Codecov Report

Merging #3721 into master will decrease coverage by 0.2%.
The diff coverage is 100%.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/kustomize.go	73.8% <100%> (+1.3%)	⬆️
pkg/skaffold/util/term.go	50% <0%> (-50%)	⬇️
pkg/skaffold/color/formatter.go	90% <0%> (-10%)	⬇️
pkg/skaffold/initializer/analyze/analyze.go	89.09% <0%> (-2.58%)	⬇️
pkg/skaffold/build/custom/script.go	52.38% <0%> (-1.47%)	⬇️
pkg/skaffold/deploy/helm.go	77.47% <0%> (-1.18%)	⬇️
pkg/skaffold/update/update.go	34.37% <0%> (-1.11%)	⬇️
pkg/skaffold/runner/dev.go	66.66% <0%> (-0.63%)	⬇️
pkg/skaffold/build/parallel.go	93.93% <0%> (-0.43%)	⬇️
pkg/skaffold/initializer/config.go	100% <0%> (ø)	⬆️
... and 12 more

[tejal29]

Thank you for your PR! This looks really great, except for some nits. If you append Env to Envs you don't need the extra AbosultePath func.

Thank you! looking forward to get this in!

[nicknovitski]

Thanks for your suggestions, I've added them.