Add Parent FlagSet

[fahedouch]

support pFlag AddParentFlagSet (spf13/pflag#357)
Signed-off-by: fahed dorgaa fahed.dorgaa@gmail.com

[AkihiroSuda]

Needs unit testing.

Also, not sure whether changing the default behavior is allowed. Probably this should be configurable.

[jpmcb]

Can you give a broader description of this change and what use case it's trying to solve?

Also, I'm assuming this is a subset of this PR? spf13/pflag#357 We would need to wait for a new pflag release and then consume it from the upstream.

[github-actions]

The Cobra project currently lacks enough contributors to adequately respond to all PRs. This bot triages issues and PRs according to the following rules:

• After 60d of inactivity, lifecycle/stale is applied. - After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied and the PR is closed.
  You can:
• Make a comment to remove the stale label and show your support. The 60 days reset. - If a PR has lifecycle/rotten and is closed, comment and ask maintainers if they'd be interested in reopening.

[marckhouzam]

As we have very few maintainers, and those have very little time, we've decided to remove the auto-close configuration.
I'm re-opening this PR since it was closed automatically.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}