Unfortunately, that's the best we have to work with (in a any version that keeps the uncropped pixels), once history is gone.
You can always put in a feature request for Photoshop, but of course that isn't going to help you today.
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I have found a solution by myself that is "pixel-perfect".
To get handles (that snaps in) on the edges for the straighten-tool, do the following:
1) Select the layer you want to straighten to 0°
2) Go to Edit/Transform/Distort. This allows to have handles on the edges. Once the handles appears, create 2 guides for every edge to create a crossing point (in fact 2 edges will suffice for straighten)
3) Then use the straighten tool. It will snap in at the crossing points. Connect to edges on the horizontal-direction.