Command for cloning an existing instance

[AkihiroSuda]

Description

CLI syntax

• Option 1: limactl clone <OLDINST> <NEWINST>
• Option 2: limactl create --name=<NEWINST> copy://<OLDINST>

I'm inclined to the latter one, but the copy:// prefix needs a bikeshedding.

Implementation

It seems to just work fine by copying the instance directory.
On APFS, clonefile(2) can be attempted by using https://pkg.go.dev/github.com/containerd/continuity@v0.4.5/fs#CopyDir

Maybe vz-identifier file should be removed?

[jandubois]

CLI syntax

• Option 1: limactl clone <OLDINST> <NEWINST>
• Option 2: limactl create --name=<NEWINST> copy://<OLDINST>

I'm inclined to the latter one, but the copy:// prefix needs a bikeshedding.

I much prefer the first option. I seems much clearer and doesn't depend on inventing another URL scheme.

Very old discussion about this at #158 (comment) and further down, which suggested limactl start NEWINST --from OLDINST (we didn't have create at that time).

But I think clone is much better. If we can create a separate command for restart, then we can afford a separate command for clone. 😄

Maybe vz-identifier file should be removed?

Also protected.