Add logic to the close command

If start and end point of a set of 2d edges coincide; create a wire directly.
If there is a distance between start and end point; add a line segment before creating the wire.

cadquery/cq.py

@@ -1773,7 +1773,14 @@ def close(self):
 
             s = Workplane().lineTo(1,0).lineTo(1,1).close().extrude(0.2)
         """
-        self.lineTo(self.ctx.firstPoint.x, self.ctx.firstPoint.y)
+        endPoint = self._findFromPoint(False)
+        startPoint = self.ctx.firstPoint
+
+        # Check if there is a distance between startPoint and endPoint
+        # that is larger than what is considered a numerical error.
+        # If so; add a line segment between endPoint and startPoint
+        if endPoint.sub(startPoint).Length > 1e-6:
+            self.lineTo(self.ctx.firstPoint.x, self.ctx.firstPoint.y)
 
         # Need to reset the first point after closing a wire
         self.ctx.firstPoint=None

tests/TestCadQuery.py

@@ -1595,3 +1595,15 @@ def testExtrude(self):
         self.assertTupleAlmostEquals(delta.toTuple(),
                                      (0.,0.,2.*h),
                                      decimal_places)
+
+    def testClose(self):
+        # Close without endPoint and startPoint coincide.
+        # Create a half-circle
+        a = Workplane(Plane.XY()).sagittaArc((10, 0), 2).close().extrude(2)
+
+        # Close when endPoint and startPoint coincide.
+        # Create a double half-circle
+        b = Workplane(Plane.XY()).sagittaArc((10, 0), 2).sagittaArc((0, 0), 2).close().extrude(2)
+
+        # The b shape shall have twice the volume of the a shape.
+        self.assertAlmostEqual(a.val().wrapped.Volume * 2.0, b.val().wrapped.Volume)