Add -o CLI flag to documentation

[dijitali]

Describe the solution you'd like
It would be useful to be able to change the output format of the Velero CLI so that the CLI can be used in higher-level orchestration tools and scripts.

Anything else you would like to add:
Something similar to the kubectl output options would probably meet a wide range of use cases.

Environment:

• Velero version (use velero version): v1.0.0
• Kubernetes version (use kubectl version): version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.2", GitCommit:"66049e3b21efe110454d67df4fa62b08ea79a19b", GitTreeState:"clean", BuildDate:"2019-05-16T18:55:03Z", GoVersion:"go1.12.5", Compiler:"gc", Platform:"darwin/amd64"}
• Kubernetes installer & version: Google Cloud SDK
• Cloud provider or hardware configuration: GCP/GKE
• OS (e.g. from /etc/os-release): OSX 10.14.5

[dijitali]

As I finished typing this I realised there's already a pretty good way to do this: output the CRD directly from kubectl.

🤦‍♂️

e.g. to list the most recent backup:

✗ kubectl get backups.velero.io --sort-by=.metadata.creationTimestamp -o jsonpath="{.items[-1].metadata.name}
daily-prod-backup-20190603040038

This handles my use-case so I'm closing this issue.

[skriss]

FYI - you can also do velero backup get -o yaml or velero backup get -o json :)

[dijitali]

@skriss - that's probably tidier. There's no mention of it in the documentation or velero --help, any chance it could be added (and any other undocumented flags)?

[skriss]

It's documented in the help for the specific commands (velero backup get --help). We can see if there's a place in the docs site where that would belong.

[skriss]

@nrb @carlisia @prydonius do you think we need to document this any further? On reflection I think it's properly documented in the CLI help text, so I'm not sure there's anything else to do here.

[nrb]

IMO it's more useful directly on the subcommands than on velero itself, which doesn't really do anything. So I'd agree we don't need to do anything.

[dijitali]

Fine by me; I think this was really my mistake in not looking at the specific command's help text.