v2 feature: Add Destination for StringSliceFlag

[davidsbond]

Checklist

• Are you running the latest v2 release? The list of releases is here.
• Did you check the manual for your release? The v2 manual is here
• Did you perform a search about this feature? Here's the Github guide about searching.

What problem does this solve?

• My team want to start using the Destination values on flags so we can have our flag values strongly typed rather than stringly typed (i.e calling c.String("flag") etc.). I noticed that the StringSliceFlag does not have a Destination field like other flags do

Solution description

• Solution would be to add a Destination field to StringSliceFlag that works the same as all other Destination flag fields do.

[saschagrunert]

I think this might be a valuable addition :)

[coilysiren]

See also => #603 🙂

[tboerger]

Did you perform a search about this feature? Here's the Github guide about searching.

Not really searched for that, right? Till yesterday that issue have been even open and have been closed for being a duplicate of this issue here... https://github.com/urfave/cli/issues?q=is%3Aissue+StringSliceFlag+Destination+is%3Aclosed

[coilysiren]

@tboerger sorry you're having a hard time with the duplication thing! Is there something specific that you want here?

[davidsbond]

@tboerger Sorry, obviously I didn't search very hard when I raised this. Agree mine should've been closed and yours left open. Happy for either issue to be used as long as it results in the feature being implemented.

[davidsbond]

@lynncyrin I have some free tech time at work tomorrow so I can look into implementing this

[tboerger]

It's more about the communication than marking something duplicate. The initial issue has been marked as claimed, which sounds like somebody would work on that, after some time nothing happened and I actively asked if I can help somehow as this lib is massively used in projects I'm involved and I haven't received any response. Just with the closing as duplicate comment I have seen that the claimed label have been removed.

I would just expect a tiny comment if somebody offers help. They issue is already nearly three years old.

[davidsbond]

@tboerger I see what you mean. Well I'll be looking to raise a PR to add this functionality sometime tomorrow, unless you'd like to do so yourself.

I also notice there are a few more flags missing the Destination field. It might be worth aggregating all those and doing a single issue for missing Destination fields.

[tboerger]

Go ahead, I would be happy to help testing.

[coilysiren]

Got it 👍 it wasn't previously clear to me that there's so much social complexity here 🙏

@davidsbond I just assigned this to you 👍

[davidsbond]

@lynncyrin @tboerger I think my PR is ready for review. Appears to work in my testing

[coilysiren]

This should go out in version 2.2.0 whenever someone feels so compelled to make another release