bug report: shell completion doesn't work with sub-commands v3-alpha4

[yogeshlonkar]

Checklist

• Are you running the latest v3 release? The list of releases is here.
• Did you check the manual for your release? The v3 manual is here. Could not find the manual, link points to 404
• Did you perform a search about this feature? Here's the GitHub guide about searching.

What problem does this solve?

If fixed, shell completion of sub-commands should work same as v2. For example:

mycli sub1 --generate-shell-completion

Instead of calling/ completing sub1 command the cli executes the action of sub1.

The issue is here https://github.com/urfave/cli/blob/v3.0.0-alpha4/help.go#L448-L455.

• --generate-shell-completion is popped from arguments slice when checkShellCompleteFlag is run for mycli
• In next recursive execution of Run for sub1 function checkShellCompleteFlag returns false as there is no --generate-shell-completion

Solution description

• A separate recursive function is needed to find the last sub-command in chain.
• If argument slice contains --generate-shell-completion the the last sub-command directly should be invoked for completion as it doesn't need chaining
• Else Run should continue with existing steps

If the solution correct, I will try to provide a PR for this

[dearchap]

@yogeshlonkar This issue is present only in v3. If you look at v2 the shellComplete flag is set in context which is used to check later on. If you can add the flag back into context that would be great

[dearchap]

@yogeshlonkar try this fix and see if it helps