Merge branch 'jk/delete-modechange-conflict' into maint

Merging a branch that removes a path and another that changes the mode bits on the same path should have conflicted at the path, but it didn't and silently favoured the removal. * jk/delete-modechange-conflict: merge: detect delete/modechange conflict t6031: generalize for recursive and resolve strategies t6031: move triple-rename test to t3030