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Igor Rivin
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The answer to the question as stated is NO. Indeed, consider (the boundary of) a tetrahedron (or any convex polyhedron). Since the cone angles at the vertices are smaller than $2\pi,$ no geodesic can be continued past a vertex (since then it would subtend an angle of smaller than $\pi$ on at least one side, and so would not be locally shortest.

Igor Rivin
  • 96.4k
  • 11
  • 153
  • 366