Implement limactl clone

[AkihiroSuda]

limactl clone OLDINST NEWINST clones an instance.

Not to be confused with limactl copy SRC DST (copy files).

Fix #3658

[jandubois]

Sorry, don't have time to do a full review right now, so just one comment.

Also, if you think clone is too similar to copy, then maybe we can use duplicate (with short alias dup). But I think clone is fine too.

[AkihiroSuda]

Also, if you think clone is too similar to copy, then maybe we can use duplicate (with short alias dup). But I think clone is fine too.

"clone" corresponds to the lingo used by VMware, VirtualBox, etc.

[Copilot]

Pull Request Overview

This PR adds a new limactl clone command to duplicate existing Lima instances by copying most files while skipping or nullifying instance-specific artifacts.

• Introduces file‐filtering lists (SkipOnClone, NullifyOnClone, TmpFileSuffixes) and wires them into both the stop and clone implementations
• Updates Darwin VM logic to regenerate an empty or missing VzIdentifier
• Adds the Cobra command, flags and end‐to‐end test cases for limactl clone

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/vz/vm_darwin.go	Regenerate empty or missing VzIdentifier on clone
pkg/store/filenames/filenames.go	Define skip/nullify lists and tmp suffixes for cloning
pkg/instance/stop.go	Reuse TmpFileSuffixes when cleaning up stopped instances
pkg/instance/clone.go	Core clone logic: directory walk, file skip, nullify and copy
hack/test-templates.sh	Enable and implement a basic clone test in CI templates
cmd/limactl/main.go	Wire newCloneCommand into the root Cobra app
cmd/limactl/copy.go	Clarify help text to distinguish copy vs. clone commands
cmd/limactl/clone.go	New Cobra command, argument handling and post‐clone editing logic
cmd/limactl/editflags/editflags.go	Adjust RegisterEdit signature to accept a comment prefix
cmd/limactl/edit.go	Update call site for new RegisterEdit signature

Comments suppressed due to low confidence (1)

cmd/limactl/copy.go:30

• [nitpick] Consider using backticks for code references in help text (e.g. limactl clone) to match existing formatting conventions.

Not to be confused with 'limactl clone'.

[alexandear]

Do we need to include an example, like we did for the copy command?

lima/cmd/limactl/copy.go

Lines 24 to 30 in 2f4aeda

	const copyHelp = `Copy files between host and guest
	Prefix guest filenames with the instance name and a colon.
	Example: limactl copy default:/etc/os-release .
	Not to be confused with 'limactl clone'.

[AkihiroSuda]

clone OLDINST NEWINST should suffice