"Triangulate" option not compatible with "Shape-Keys" (morph) animations

Moved from https://github.com/godotengine/godot/issues/1312, originally by @SuperUserNameMan:

> The "Triangulate" option of the Better Collada Exporter is not really compatible with "Shape-Keys" (morph) animations.
>
> If the "shape-key" animated mesh contains polygons other than triangles, and if it is exported with "triangulate" option set to ON, then, once imported into Godot, the vertices of each morph targets won't match. (I tried with a simple deformed cube)
>
> If you re-export it with "triangulate" to OFF, then, Godot will warn you about "Primitive polygon not well supported (concave shape may fail)".
>
> The only workaround i've found is to triangulate the mesh using a modifier into Blender, just before creating the Shape-keys.