Allow command aliasing via PATH lookup

[jandubois]

There have been several requests to add additional aliases to limactl commands, e.g. ps for list or ssh for shell.

Instead of adding more and more personal aliases into the app itself, I would like to see a generic command aliasing mechanism like git and kubectl already implement:

When a subcommand foo does not exist then limactl will look for limactl-foo on the PATH, and execute that program instead (passing all commandline arguments along).

Let's assume we add --running filter to the list subcommand, then a user could create limactl-ps:

#!/bin/sh
limactl list --running "$@"

[nirs]

Sounds like the right way!

[AkihiroSuda]

Instead of adding more and more personal aliases into the app itself, I would like to see a generic command aliasing mechanism like git and kubectl already implement:

What are pros (and cons) of making them subcommands of git/kubectl/limactl, not independent commands?

[jandubois]

The main reason for the subcommands is that people have claimed they expected a certain alias to work, so they just typed it subconsciously.

E.g. when working mostly with docker and using docker ps to list containers, it feels natural to run limactl ps to list machines.

When you make it a different command, you still have to think about it and type the correct command. Then you can also just remember to type limactl ls.

@nirs explained that the same happens to him that he types limactl ssh instead of limactl shell.

We discussed different ways to accomplish this on Slack, and using this plugin mechanism seems like a well established pattern and seems fairly simple to implement.

[AkihiroSuda]

Aliasing ssh=shell should be fine and can be just implemented in the upstream, but aliasing ps=ls seems weird.

If we are going to have limactl ps, that should diverge from limactl ls and should print information specifically about running instances.

[nirs]

Added #3613 to get more input on this. This is also easy task for new contributors.

[jandubois]

Aliasing ssh=shell should be fine and can be just implemented in the upstream, but aliasing ps=ls seems weird.

I replied in #3613 why I think aliasing ssh to shell is also weird.

If we are going to have limactl ps, that should diverge from limactl ls and should print information specifically about running instances.

Yes, but I don't think we should have a ps subcommand at all. We should add a --running option (and maybe --stopped or allow --running=false as well) to list.

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But this issue is really about providing a plugin mechanism similar to git, gh, kubectl, docker, helm, kustomize, terraform (I'm sure there are plenty more).

The discussion about the specific examples is really a distraction; what is the argument why limactl should not support a similar plugin mechanism?