Blender Git Loki

Cycles-Bake: external saving is working again (though there is no UI)

Right now you can set it via the operator or via the scene properties:
bpy.ops.object.bake(filepath="/tmp/baked.png", save_mode='EXTERNAL', use_split_materials=True, ...)

bpy.context.scene.render.bake.filepath = "/tmp/baked.png"
bpy.context.scene.render.bake.save_mode = 'EXTERNAL'
bpy.context.scene.render.bake.use_split_materials = True # or False