Now you can join multiple wires all at once

src/Mod/Draft/Draft.py

@@ -1339,7 +1339,20 @@ def extrude(obj,vector,solid=False):
     FreeCAD.ActiveDocument.recompute()
     return newobj
 
-def joinWires(wire1, wire2):
+def joinWires(wires, joinAttempts = 0):
+    if joinAttempts > len(wires):
+        return FreeCAD.ActiveDocument.recompute()
+    joinAttempts += 1
+    for wire1Index, wire1 in enumerate(wires):
+        for wire2Index, wire2 in enumerate(wires):
+            if wire2Index <= wire1Index:
+                continue
+            if not joinTwoWires(wire1, wire2):
+                wires.pop(wire2Index)
+                break
+    joinWires(wires, joinAttempts)
+
+def joinTwoWires(wire1, wire2):
     wire1AbsPoints = [wire1.Placement.multVec(point) for point in wire1.Points]
     wire2AbsPoints = [wire2.Placement.multVec(point) for point in wire2.Points]
     if wire1AbsPoints[0] == wire2AbsPoints[0]:
@@ -1349,10 +1362,13 @@ def joinWires(wire1, wire2):
         wire2AbsPoints = list(reversed(wire2AbsPoints))
     elif wire1AbsPoints[-1] == wire2AbsPoints[-1]:
         wire2AbsPoints = list(reversed(wire2AbsPoints))
+    elif wire1AbsPoints[-1] == wire2AbsPoints[0]:
+        pass
+    else:
+        return False
     wire2AbsPoints.pop(0)
     wire1.Points = [wire1.Placement.inverse().multVec(point) for point in wire1AbsPoints] + [wire1.Placement.inverse().multVec(point) for point in wire2AbsPoints]
     FreeCAD.ActiveDocument.removeObject(wire2.Name)
-    FreeCAD.ActiveDocument.recompute()
 
 def fuse(object1,object2):
     '''fuse(oject1,object2): returns an object made from

src/Mod/Draft/DraftTools.py

@@ -3234,7 +3234,7 @@ class Join(Modifier):
             print(FreeCADGui.Selection.getSelection())
             FreeCADGui.addModule("Draft")
             self.commit(translate("draft","Upgrade"),
-                ['Draft.joinWires(FreeCADGui.Selection.getSelection()[0], FreeCADGui.Selection.getSelection()[1])', 'FreeCAD.ActiveDocument.recompute()'])
+                ['Draft.joinWires(FreeCADGui.Selection.getSelection())', 'FreeCAD.ActiveDocument.recompute()'])
         self.finish()