Removed hard-coded "kn" in usage/error messages

[rhuss]

Instead use argv[0], the first argument provided on the command line. If the command is called with a path, that path should be stripped off from the given argument.

See #1175 for more context.

[github-actions]

This issue is stale because it has been open for 90 days with no
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inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[rhuss]

/good-first-issue
/remove-lifecycle stale

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/good-first-issue
/remove-lifecycle stale

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[hzliangbin]

/assign

[hzliangbin]

@rhuss hi, plz let me know if I could take this issue? thanks.

[rhuss]

@hzliangbin That's great ! Please go ahead and take this issue.

[hzliangbin]

@rhuss sorry for being late.

kn in root cmd usage and help should be modified too?

[rhuss]

no worries.

@hzliangbin yes, ideally everywhere where kn is hardcoded, that should be replaced by the real command name, without path.

[rhuss]

@hzliangbin happy new year ;-) Do you have any news on this issue ? No worries if you hadn't any time yet, but we want to tackle this story possibly for the next release.

[hzliangbin]

@rhuss sorry. haven't got any new ideas.

[rhuss]

No worries. If you don't mind, I would unassign you from this issue and add you as a reviewer when a PR comes in ?

[itsmurugappan]

/assign