jj diffedit doesn't allow restoring conflicts

[scott2000]

Description

I noticed this while writing a test case for #4951: if you run jj diffedit on a merge commit that resolves a conflict and undo the resolution, then the conflict markers are restored as text, but the commit isn't marked as conflicted. This is unintuitive, because it seems like the commit should become conflicted again when restoring a conflict.

Steps to Reproduce the Problem

1. Create a merge commit with a conflict.
2. Resolve the merge conflict in the working copy.
3. Run jj diffedit with the builtin editor, and press "c" without selecting any changes.
4. Run jj diff and jj status

Expected Behavior

jj diff shows no changes, and jj status reports the working copy as conflicted, since the conflict resolution was undone.

Actual Behavior

jj diff shows no changes, but jj status reports the conflict as resolved. The conflict markers are committed in the working copy as text.

Specifications

• Platform: NixOS unstable
• Version: jj 0.23.0-81251c9382069c122b73f88af69a7fc1bdddbe07