This pull request updates the YAML library used in Helmfile from goccy/go-yaml to gopkg.in/yaml.v3, along with associated code changes to reflect this migration. It removes support for goccy/go-yaml and its related functionality, ensuring that yaml.v3 is the default library in Helmfile v1.x. The changes span multiple files, including configuration, runtime logic, tests, and documentation.

YAML Library Migration:

• Updated the YAML library from goccy/go-yaml to gopkg.in/yaml.v3 across the codebase. (pkg/runtime/runtime.go, pkg/yaml/yaml.go, go.mod) [1] [2] [3]
• Removed the environment variable HELMFILE_GOCCY_GOYAML and replaced it with HELMFILE_GO_YAML_V3 to toggle between yaml.v2 and yaml.v3. (pkg/envvar/const.go, docs/index.md) [1] [2]
• Modified YAML encoding and decoding methods to use yaml.v3 features, including strict field validation and indentation settings. (pkg/yaml/yaml.go)

Test Updates:

• Updated test cases to reflect the migration to yaml.v3, including renaming variables and test descriptions. (pkg/app/app_test.go, pkg/app/app_template_test.go, pkg/tmpl/context_funcs_test.go, pkg/yaml/yaml_test.go) [1] [2] [3] [4]
• Removed tests and functionality related to JSON-style YAML encoding, which was specific to goccy/go-yaml. (pkg/tmpl/context_funcs_test.go)

Documentation Updates:

• Updated the documentation to reflect the removal of goccy/go-yaml and the introduction of yaml.v3 as the default YAML library. (docs/index.md)

Dependency Management:

• Removed goccy/go-yaml from direct dependencies and added gopkg.in/yaml.v3 to the project. (go.mod) [1] [2]

These changes ensure compatibility with yaml.v3 while simplifying the codebase by removing support for goccy/go-yaml.