Revert "Revert "Update testtool change detection""

This reverts commit e75b41aec1.

tools/testtool/commands/deadlines.go

@@ -17,6 +17,7 @@ type (
 	Task struct {
 		Name  string   `yaml:"task"`
 		Score int      `yaml:"score"`
+		Watch []string `yaml:"watch"`
 	}
 
 	Group struct {
@@ -34,6 +35,16 @@ func (g Group) IsOpen() bool {
 	return time.Until(t) < 0
 }
 
+func (d Deadlines) Tasks() []*Task {
+	var tasks []*Task
+	for _, g := range d {
+		for i := range g.Tasks {
+			tasks = append(tasks, &g.Tasks[i])
+		}
+	}
+	return tasks
+}
+
 func (d Deadlines) FindTask(name string) (*Group, *Task) {
 	for _, g := range d {
 		for _, t := range g.Tasks {
@@ -80,11 +91,19 @@ func findChangedTasks(d Deadlines, files []string) []string {
 		}
 
 		_, task := d.FindTask(components[0])
-		if task == nil {
+		if task != nil {
+			tasks[task.Name] = struct{}{}
 			continue
 		}
 
+		for _, task := range d.Tasks() {
+			for _, path := range task.Watch {
+				if components[0] == path {
 					tasks[task.Name] = struct{}{}
+					continue
+				}
+			}
+		}
 	}
 
 	var l []string