incus/network: add dynamic command line completions

[adamcstephens]

The shell handles the filtering for you, but we could try and filter by remote name for example in class someone hits tab again.

I'll probably finish building out network to see if I can just reuse this function or the bulk of it, but this is a start. Done.

Example

─❯ incus network show <TAB>
bond0    fast1           incus1:fast0  incus1:oob0      oob0
bridge0  incus1:bond0    incus1:fast1  incus1:vlan2010  vlan2010
fast0    incus1:bridge0  incus1:lo     lo

One can also explore these directly

─❯ go run ./cmd/incus __complete network show ""
incus1:lo
incus1:oob0
incus1:bond0
incus1:bridge0
incus1:vlan2010
incus1:fast0
incus1:fast1
lo
oob0
bond0
bridge0
vlan2010
fast0
fast1
:4
Completion ended with directive: ShellCompDirectiveNoFileComp

[adamcstephens]

This is far from a full set of dynamic completions, but this is a good start and handles all of the basic network subcommands and config show (as a proof of concept that the functions can be reused).

Marking as ready to review so I can get some feedback.

[stgraber]

Looking pretty good. Just the hardcoded local which should be replaced by the variable for the default remote.

As someone who runs with well over a dozen different remotes, a bunch of those being clusters with hundreds of instances and some of which requiring VPNs, I don't know that completing across all remotes is necessarily the right thing to do though :)

It may make more sense to only complete over the current default remote and motivate folks to incus remote switch as needed if they expect to do a bunch of interactions against a specific remote.

[adamcstephens]

Thanks for the feedback. I was a bit worried about the performance impact of iterating all the remotes, but hadn't thought of a better way. Now that I understand how this all works a bit better though, you inspired me to a nicer solution.

The changes I just pushed switch it so that if you haven't typed a remote (no colon in the entry), it'll suggest all the default resources plus all the available remote names. Once you have typed the colon (or tab completed it), and hit tab again, it will query the named remote for the resources. This should provide the benefit of not hitting endpoints until requested, but still allowing for tab completion for those remotes.

[adamcstephens]

With an example:

─❯ ~/go/bin/incus network attach <TAB>
bond0    fast0  incus1:  local:  test1
bridge0  fast1  lo       oob0    vlan2010
─❯ ~/go/bin/incus network attach incus1:<TAB>
incus1:enp5s0  incus1:incusbr0  incus1:lo

[stgraber]

Oh neat, that's definitely the best of all worlds!

[stgraber]

Thanks, very cool work!