We initially opened #7445 as a proof-of-concept for using worktrees to detect conflicts as part of a rebase, and if we are happy with shipping this to address #6960 we should apply this same approach to our existing merge conflict detection.

This will address at least two known issues with our current git merge-tree approach:

• Incorrectly reporting "there will be conflicting files" #5664 - incorrectly reporting there will be conflicts
• merge hint doesn't seem to follow renames when using git-merge-tree #5568 - incorrectly reporting the number of conflicted files

The worktree approach is favourable here because it lets us rely on Git's behaviour when merging and rebasing, rather than using an approximation. It should also let us perform the work while not affecting the user's working directory.