bin/60383: fssconfig(8): distinguish between taking and loading a snapshot

["campbell+netbsd%mumble.net@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60383
>Category:       bin
>Synopsis:       fssconfig(8): distinguish between taking and loading a snapshot
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 29 02:30:00 +0000 2026
>Originator:     Taylor R Campbell
>Release:        current, 11, 10, 9, ...
>Organization:
The NetFSS Foundasnapshot, Inc.
>Environment:
>Description:

	The way to create a new snapshot /fs/.snap/20260628 archiving
	the current state of a file system /fs, and configure fss0 to
	point at it, is:

		fssconfig fss0 /fs /fs/.snap/20260628

	The way to load an existing snapshot /fs/.snap/20260628
	recovering a past state of the file system /fs is:

		fssconfig fss0 /fs /fs/.snap/20260628

	Yes, those are the same command.

	This is confusing and error-prone: what operation we are
	_trying_ to do should not depend on what files exist on disk.

	When _creating_ a snapshot, fssconfig(8) should be able to
	report an error if the file already exists.

	When _loading_ a snapshot, fssconfig(8) should be able to
	report an error if the file does not actually exist.

>How-To-Repeat:

	try to use ffs fss snapshots (say that five times fast!)

>Fix:

	Yes, please!

	Perhaps we should have separate options like -C and -L for
	`create' and `load'.