autodig chattiness

The autodig code still requires lots of interaction, because of all the
digging messages.  Make these messages behave more like boulder pushing
messages, where they only display if the previous move wasn't a push.

include/decl.h

@@ -200,7 +200,8 @@ E NEARDATA struct dig_info {		/* apply.c, hack.c */
 	int	effort;
 	d_level level;
 	coord	pos;
-	boolean down, chew, warned;
+	long lastdigtime;
+	boolean down, chew, warned, quiet;
 } digging;
 
 E NEARDATA long moves, monstermoves;

src/dig.c

@@ -353,7 +353,7 @@ dig()
 		    feel_location(dpx, dpy);
 		else
 		    newsym(dpx, dpy);
-		if(digtxt) pline(digtxt);	/* after newsym */
+		if(digtxt && !digging.quiet) pline(digtxt); /* after newsym */
 		if(dmgtxt)
 		    pay_for_damage(dmgtxt);
 
@@ -378,6 +378,8 @@ dig()
 			newsym(dpx, dpy);
 		}
 cleanup:
+		digging.lastdigtime = moves;
+		digging.quiet = FALSE;
 		digging.level.dnum = 0;
 		digging.level.dlevel = -1;
 		return(0);
@@ -878,21 +880,32 @@ struct obj *obj;
 						"chopping at the door",
 						"cutting the tree"
 			};
+			did_dig_msg = FALSE;
+			digging.quiet = FALSE;
 			if (digging.pos.x != rx || digging.pos.y != ry ||
 			    !on_level(&digging.level, &u.uz) || digging.down) {
+			    if (flags.autodig && !dig_target && !digging.down &&
+				digging.pos.x == u.ux &&
+				digging.pos.y == u.uy &&
+				(moves <= digging.lastdigtime+2 &&
+				 moves >= digging.lastdigtime)) {
+				/* avoid messages if repeated autodigging */
+				did_dig_msg = TRUE;
+				digging.quiet = TRUE;
+			    }
 			    digging.down = digging.chew = FALSE;
 			    digging.warned = FALSE;
 			    digging.pos.x = rx;
 			    digging.pos.y = ry;
 			    assign_level(&digging.level, &u.uz);
 			    digging.effort = 0;
-			    You("start %s.", d_action[dig_target]);
+			    if (!digging.quiet)
+				You("start %s.", d_action[dig_target]);
 			} else {
 			    You("%s %s.", digging.chew ? "begin" : "continue",
 					d_action[dig_target]);
 			    digging.chew = FALSE;
 			}
-			did_dig_msg = FALSE;
 			set_occupation(dig, "digging", 0);
 		}
 	} else if (Is_airlevel(&u.uz) || Is_waterlevel(&u.uz)) {