API for shared arguments is a bit weird

[sgrif]

So diesel_cli has a use case where basically all of our commands take the same argument. You can see our exact code here: https://github.com/sgrif/diesel/blob/331f81c353ec0c7f0b6897cb80cb405b2d9120bb/diesel_cli/src/main.rs#L13-L42

All of our commands except one take --database-url (and really it's not a big deal if it gets passed to that command as well). Right now, if I put that argument on the Clap::App instance, it requires that the command is run as diesel --database-url=url migration run, but I'd much rather it be diesel migration run --database-url=url, or really just allow it basically anywhere. (As an aside, we're having to wrap the argument in a closure because Arg doesn't derive Clone, but it probably could)

Does this seem like a reasonable/common enough use case to warrant support within clap itself?

[kbknapp]

If you add that Arg to your top level App instance but set the Arg::global(true) it should be exactly what you're looking for...i.e. it'll just propagate that particular Arg down through all child subcommands....if not it's a bug ;)

[kbknapp]

@sgrif Also I haven't forgotten about #372 I'm really hoping to have it out really soon with the 2.x base 😉

[kbknapp]

@sgrif Also I forgot to mention that in v2 it supports passing borrowed Arg structs, so you could create an Arg instance and just pass a borrow of that same instance to all your subcommands which doesn't require Cloneing like global(true) does in 1.x (Arg::global also exists in v2 and removes the Cloneing as well, just FYI it's essentially shorthand for passing a borrow to down through each subcommand Edit: Arg::global still clones, I was mistaken on how'd I'd implemented that...but passing a borrow does not clone so long as global(true) is not set).

Edit: Corrections

[sgrif]

Yup, I just missed this. Thanks.