why? because people want it (#10719)

core/src/mindustry/ai/types/MinerAI.java

@@ -71,5 +71,8 @@ public class MinerAI extends AIController{
 
             circle(core, unit.type.range / 1.8f);
         }
+        if(!unit.type.flying){
+            unit.updateBoosting(unit.type.boostWhenMining || unit.floorOn().isDuct || unit.floorOn().damageTaken > 0f || unit.floorOn().isDeep());
+        }
     }
 }

core/src/mindustry/type/UnitType.java

@@ -169,6 +169,8 @@ public class UnitType extends UnlockableContent implements Senseable{
     canBoost = false,
     /** if true, this unit will always boost when using builder AI */
     boostWhenBuilding = true,
+    /** if true, this unit will always boost when using miner AI */
+    boostWhenMining = true,
     /** if false, logic processors cannot control this unit */
     logicControllable = true,
     /** if false, players cannot control this unit */
@@ -974,6 +976,9 @@ public class UnitType extends UnlockableContent implements Senseable{
                 if(buildSpeed > 0f){
                     commands.add(UnitCommand.rebuildCommand, UnitCommand.assistCommand);
                 }
+                if(mineTier > 0){
+                    commands.add(UnitCommand.mineCommand);
+                }
             }
 
             //healing, mining and building is only supported for flying units; pathfinding to ambiguously reachable locations is hard.