skaffold credits

[balopat]

Description

This will be a new command skaffold credits:

skaffold help
...

Other Commands:
  completion        Output shell completion for the given shell (bash or zsh)
  config            Interact with the Skaffold configuration
  credits           Export third party notices to given path (current dir by default)
  diagnose          Run a diagnostic on Skaffold
  version           Print the version information

skaffold credits --help                                                                                                                                                                                                                    4604ms  Thu 31 Oct 2019 01:20:30 PM PDT
Export third party notices to given path (./skaffold-credits by default)

Examples:
  # export third party licenses to ~/skaffold-credits
  skaffold credits -d ~/skaffold-credits

Options:
  -d, --dir='./skaffold-credits': destination directory to place third party licenses

Usage:
  skaffold credits [flags] [options]

Use "skaffold options" for a list of global command-line options (applies to all commands).

This is using two new tools:

• licenses script from github.com/google/trillian to automatically list the licenses
• rakyll/statik for embedding the notices file

The flow includes now generating the sources for embedding before every binary creation command.

User facing changes

Before

No skaffold credits command.

After

See new command above.

Next PRs.

none.

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

`skaffold credits` - skaffold now exposes third party licenses recursively  that you can export in the form of a tgz file. 

[codecov]

Codecov Report

Merging #3138 into master will increase coverage by <.01%.
The diff coverage is 80%.

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/credits_dummy.go	0% <0%> (ø)
cmd/skaffold/app/cmd/credits.go	100% <100%> (ø)
cmd/skaffold/app/cmd/cmd.go	67.18% <100%> (+0.25%)	⬆️

[tejal29]

few nits