Update Cobra to v1.5.0

[rolinh]

Cobra v1.5.0 is now released and with it comes a new API called flag groups that allows to mark flags as mutually exclusive or required together.

This PR gives it a go but other than saving a couple of lines of code, I'm not convince by the change from a user perspective.

Current output:

$ hubble observe --first 42 --all
cannot set both --first and --all

With this patch:

$ hubble observe --first 42 --all
if any flags in the group [first all] are set none of the others can be; [all first] were all set

Note that this new Cobra release also brings another new feature called active help. I'm not yet sure how it'd be best used in the context of the Hubble CLI.

EDIT: I ended up not opting for the new flag groups feature and removed the commit.

[kaworu]

$ hubble observe --first 42 --all
if any flags in the group [first all] are set none of the others can be; [all first] were all set

I find this error message more confusing than before the patch, unfortunately it cannot be customized: https://github.com/spf13/cobra/blob/5f2ec3c897155c3346e77430932e3966e5cfa648/flag_groups.go#L160. Let's see what other people think.

Also side question: aren't --all and --last also mutually exclusive?

[tklauser]

$ hubble observe --first 42 --all
if any flags in the group [first all] are set none of the others can be; [all first] were all set

I find this error message more confusing than before the patch, unfortunately it cannot be customized: https://github.com/spf13/cobra/blob/5f2ec3c897155c3346e77430932e3966e5cfa648/flag_groups.go#L160. Let's see what the other people think.

I agree with Alex that the previous error message is more distinct and easier to read. As long as the message cannot be customized, I think we should stick to the old way of checking mutually exclusive flags.

[rolinh]

Also side question: aren't --all and --last also mutually exclusive?

Indeed. I added a commit to handle this case.

As hinted in the PR description, I also agree that the new error message is not very clear nor succinct. I removed the commit that switched to using new flag groups.

[tklauser]

Thanks