An attempt at a no-encryption-props flag

[rincebrain]

Motivation and Context

People sometimes want to drop encryption from a dataset on send, which you can do, but right now, you can't use -R or -p with it.

This lets you get away with that.

Description

Allow you to get away with using -R and -p if you're trying to just discard encryption settings without also using -w.

I haven't added a man page update for it yet, because I'm assuming someone will think of a better shortflag than "C", and I assume we'd like actual tests added around it, but I figured I'd post it and get comments on it.

I was expecting to have to make kernel-side code changes for this to fly, tbh, but...apparently not.

How Has This Been Tested?

A bit of manual testing.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Performance enhancement (non-breaking change which improves efficiency)
• [ ] Code cleanup (non-breaking change which makes code smaller or more readable)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• [ ] Documentation (a change to man pages or other documentation)

Checklist:

• [x] My code follows the OpenZFS code style requirements.
• [ ] I have updated the documentation accordingly.
• [x] I have read the contributing document.
• [ ] I have added tests to cover my changes.
• [x] I have run the ZFS Test Suite with this change applied.
• [ ] All commit messages are properly formatted and contain Signed-off-by.

[robn]

All other things being equal, I'd want any "remove encryption" option to have a big flashing light and multiple stages of "are you sure", but...

send and recv are already a usability disaster, so one more doesn't bother me so much. If people want it, let 'em have it. Even better if it can be done client side.

[shahn]

@rincebrain are you still working on this, or do you want some help with polishing it? I definitely have a usecase for it.

[rincebrain]

The complete lack of reviews means I don't care and this is going to die when I give up on it in 5 years with no reviews, like always.