The tool system now supports both pickaxes and shovels.
To use the new feature, right click the tool in the Options GUI. This will switch the tool to the equivalent shovel or pickaxe, respective to which was previously in use.
For example, a gold pickaxe with efficiency 3 will turn into a gold shovel with efficiency 3
This allows the excavator to not get stuck on dirt, gravel, etc. All you need to do is switch the tool by right clicking in the GUI.