Support alias "ranges" for commands

[jedevc]

Wanting to gauge whether this would be an accepted feature! See #66 (comment), where I saw this mentioned before. I want to implement something like the ip address command, which can be called using ip address, ip addr, ip a, etc - all prefixes of address are allowed. Manually specifying all allowed values in kong is currently very verbose, and clutters up the help.

Here's a potential proposal to allow something like this - added as an extension to aliases so that each command would need to opt into this.

Essentially, something like:

type Cmd struct {
	// aliases is extended to allow a range of valid aliases
	// the <cert> portion indicates the minimum allowed value
	// the <ificates> portion indicates optional characters
	Certificates `cmd:"" aliases:"cert|ificates"`
}

Would allow all of:

$ cmd certificates
$ cmd certificate
$ cmd cert
$ cmd certif # weird but allowed

For showing aliases in the help, we can abbreviate this to cert[ificates].

Very very happy to submit a patch for this, but wanted to see if it's a good idea first.

[alecthomas]

I'm not against it. I like that it's explicit, as that avoids my main objection against automatic prefix matching, which is the problem with backwards incompatible changes. But this is pretty nice.

What would the help look like?

[jedevc]

I'm thinking something like this? With [ificates] to indicate optionality?

$ go run . certificates --help
Usage: kong-app cert[ificates] [flags]

Though, the current aliases help looks like (for an alias cert):

$ go run . certificates --help
Usage: kong-app certificates (cert) [flags]

So potentially, instead should be this?

$ go run . certificates --help
Usage: kong-app certificates (cert[ificates]) [flags]

[alecthomas]

The first one looks way better I think