Simple cyclic dependency detection

README.md

@@ -73,6 +73,19 @@ css:
     - npm run buildcss
 ```
 
+Each task can only be run once. If it is included from another dependend task causing
+a cyclomatic dependency, execution will be stopped.
+
+```yml
+task1:
+  deps: [task2]
+
+task2:
+  deps: [task1]
+```
+
+Will stop at the moment the dependencies of `task2` are executed.
+
 ### Prevent task from running when not necessary
 
 If a task generates something, you can inform Task the source and generated

task.go

@@ -23,6 +23,8 @@ var (
 
 	// Tasks constains the tasks parsed from Taskfile
 	Tasks = make(map[string]*Task)
+
+	runTasks = make(map[string]bool)
 )
 
 func init() {
@@ -84,6 +86,11 @@ func Run() {
 
 // RunTask runs a task by its name
 func RunTask(name string) error {
+	if _, found := runTasks[name]; found {
+		return &taskRunError{taskName: name, err: fmt.Errorf("Cyclic dependency detected")}
+	}
+	runTasks[name] = true
+
 	t, ok := Tasks[name]
 	if !ok {
 		return &taskNotFoundError{name}