tools: Warp warning
I might do several warps, and then scroll back and forth in the undo stack to compare the adjustments. However, it's easy lose the warp work if you undo the initial warp action, there's no warning and no recovery. The warp was never committed.
this merge warns the user that the next undo will cancel the warp, creating a safety pause and user think. It also informs the user that the warp has been cancelled.