Add Labels to Metadata

[jlewi]

fixes: #7425
Description

• Add labels to metadata so that skaffold files can have labels identifying
  the config.

• Using labels is useful for being able to match skaffold files.

• Concretely, we want to use labels to identify the different environments
  corresponding to a skaffold file (e.g. dev/prod etc...). These labels
  our used by our CD tooling to identify the skaffold files which need to
  be built.

User facing changes (remove if N/A)

After this change users can include labels in their skaffold.yaml files; e.g.

kind: Config
metadata:
  name: some config
  labels:
     dev: "true"

[codecov]

Codecov Report

Merging #6782 (b59786c) into main (290280e) will decrease coverage by 1.09%.
The diff coverage is 65.71%.

@@            Coverage Diff             @@
##             main    #6782      +/-   ##
==========================================
- Coverage   70.48%   69.39%   -1.10%     
==========================================
  Files         515      540      +25     
  Lines       23150    24596    +1446     
==========================================
+ Hits        16317    17068     +751     
- Misses       5776     6396     +620     
- Partials     1057     1132      +75     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/deploy.go	52.00% <ø> (-1.85%)	⬇️
cmd/skaffold/app/cmd/dev.go	84.61% <0.00%> (ø)
cmd/skaffold/app/cmd/flags.go	89.00% <0.00%> (-1.82%)	⬇️
cmd/skaffold/app/cmd/render.go	36.66% <0.00%> (-4.72%)	⬇️
cmd/skaffold/skaffold.go	0.00% <ø> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.88% <50.00%> (+0.24%)	⬆️
cmd/skaffold/app/cmd/lint.go	52.94% <52.94%> (ø)
cmd/skaffold/app/cmd/cmd.go	70.49% <75.00%> (-0.57%)	⬇️
cmd/skaffold/app/cmd/delete.go	69.23% <80.00%> (+13.67%)	⬆️
cmd/skaffold/app/cmd/debug.go	100.00% <100.00%> (ø)
... and 134 more

---

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[jlewi]

Looks like the linter is failing because I updated v2beta24

Invalid changes:
----------------
diff --git a/pkg/skaffold/schema/v2beta24/config.go b/pkg/skaffold/schema/v2beta24/config.go
time="2021-10-30T22:51:36Z" level=fatal msg="structural changes detected"
index dcb198ef0..1eea3ba3a 100755
--- a/pkg/skaffold/schema/v2beta24/config.go
+++ b/pkg/skaffold/schema/v2beta24/config.go
@@ -58,6 +58,9 @@ type SkaffoldConfig struct {
 type Metadata struct {
 	// Name is an identifier for the project.
 	Name string `yaml:"name,omitempty"`
+
+	// Labels is a map of labels identifying the project.
+	Labels map[string]string `yaml:"labels,omitempty"`
 }
 
 // Pipeline describes a Skaffold pipeline.
exit status 1
FAILED hack/check-schema-changes.sh

I would expect this to be a backwards compatible change since its purely additive.

What would be the correct way to introduce this change? Should I create a new version?

[aaron-prindle]

@jlewi thanks for the submission here. Yes, creating a new schema version would be the correct thing to do in this case

[briandealwis]

As a rule, we don't make changes to previously published schema versions.

[jlewi]

Apologies; I should have checked the development guide first.
https://github.com/GoogleContainerTools/skaffold/blob/main/DEVELOPMENT.md#making-a-config-change

Might take me a couple days to follow up on this. Feel free to mark this PR as draft or wip.

[jlewi]

This updated. PTAL.

[aaron-prindle]

LGTM. Thanks adding this