Blender Git Loki

Fix T79553: StretchTo constraint: Apply Pose changes bone length

Recompute Rest Length stored in the StretchTo constraint after applying
the current pose as rest pose.

The "Apply Pose as Rest Pose" operator applies the evaluated pose as
rest pose, which means that the change in bone length from the StretchTo
constraint is applied to the rest pose. The bug was caused by the fact
that the StretchTo constraint wasn't updated for the new pose, and thus
still applied the same scale factor to the new pose, effectively
doubling its effect.

The "Apply Pose as Rest Pose" operator now forces a recompute of the
rest length cached in the StretchTo constraint data. As a result, the
length of the bone before and after the pose is applied remains the
same. The X and Z scale (perpendicular to the bone length) are reset to
1.0, as with the applied pose the bone isn't stretched or squashed any
more.