fix: Support auto-generated CLI reference doc in the notation repo

[majiayu000]

Summary

This PR fixes #859

Changes

• Added GitHub workflow to automatically generate CLI reference documentation when changes are made to cmd/notation
• Created cmd/notation/doc.go with gendoc build tag for documentation generation using cobra/doc
• Refactored cmd/notation/main.go to use !gendoc build tag and export NewRootCommand() function for reuse
• Created cmd/notation/root.go containing the NewRootCommand() function that initializes the root cobra command
• Added Makefile target cli-docs for manual CLI documentation generation
• Updated .gitignore to exclude generated docs/cli/ directory
• Updated dependencies to include github.com/spf13/cobra/doc for markdown generation

The workflow automatically creates a pull request when CLI commands change, similar to the minder project workflow referenced in the issue.

Testing

• All unit tests pass
• Build succeeds
• Manual CLI docs generation works with make cli-docs
• Generated markdown files are properly formatted

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Generated with Claude Code

[Copilot]

Pull request overview

This PR implements automatic generation of CLI reference documentation for the notation project. The implementation uses build tags to separate the documentation generation logic from the main CLI binary, and adds a GitHub Actions workflow that automatically creates pull requests when CLI commands are modified.

Key changes:

• Added GitHub workflow to auto-generate CLI documentation on changes to cmd/notation
• Introduced build tag separation (gendoc vs !gendoc) to enable dual-purpose main package usage
• Refactored root command initialization into a reusable NewRootCommand() function
• Updated dependencies to include cobra/doc for markdown generation

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
.github/workflows/update-docs-cli.yml	New workflow that triggers on cmd/notation changes and creates PRs with updated CLI docs
cmd/notation/doc.go	Documentation generation entry point using gendoc build tag
cmd/notation/main.go	Simplified to use NewRootCommand() with !gendoc build tag
cmd/notation/root.go	Extracted root command initialization logic for reuse
Makefile	Added cli-docs target for manual documentation generation
.gitignore	Excluded generated docs/cli directory from version control
go.mod	Updated cobra and pflag versions, added new indirect dependencies
go.sum	Updated checksums for new and upgraded dependencies

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[Copilot]

The import path go.yaml.in/yaml/v3 is incorrect. The correct import path for yaml.v3 is gopkg.in/yaml.v3. This appears to be introduced as an indirect dependency. Running go mod tidy should correct this to use the proper import path.

Suggested change

	go.yaml.in/yaml/v3 v3.0.4 // indirect
	gopkg.in/yaml.v3 v3.0.4 // indirect

[FeynmanZhou]

Where will the CLI reference doc to be generated? From the cmd/notation/doc.go, will the doc be generated in a new folder created in the notation repo?

[FeynmanZhou]

Thanks @majiayu000 .