Merge branch 'watch'

Author: andreynering

README.md

@@ -322,6 +322,12 @@ build   Build the go binary.
 test    Run all the go tests.
 ```
 
+## Watch tasks (experimental)
+
+If you give a `--watch` or `-w` argument, task will watch for files changes
+and run the task again. This requires the `sources` attribute to be given,
+so task know which files to watch.
+
 ## Alternatives
 
 Similar software:

cmd/task/task.go

@@ -26,6 +26,7 @@ hello:
 		pflag.PrintDefaults()
 	}
 	pflag.BoolVarP(&task.Force, "force", "f", false, "forces execution even when the task is up-to-date")
+	pflag.BoolVarP(&task.Watch, "watch", "w", false, "enables watch of the given task")
 	pflag.Parse()
 	task.Run()
 }

errors.go

@@ -36,3 +36,11 @@ type cyclicDepError struct {
 func (err *cyclicDepError) Error() string {
 	return fmt.Sprintf(`task: Cyclic dependency of task "%s" detected`, err.taskName)
 }
+
+type cantWatchNoSourcesError struct {
+	taskName string
+}
+
+func (err *cantWatchNoSourcesError) Error() string {
+	return fmt.Sprintf(`task: Can't watch task "%s" because it has no specified sources`, err.taskName)
+}

task.go

@@ -18,6 +18,8 @@ var (
 
 	// Force (--force or -f flag) forces a task to run even when it's up-to-date
 	Force bool
+	// Watch (--watch or -w flag) enables watch of a task
+	Watch bool
 
 	// Tasks constains the tasks parsed from Taskfile
 	Tasks = make(map[string]*Task)
@@ -66,6 +68,13 @@ func Run() {
 		}
 	}
 
+	if Watch {
+		if err := WatchTasks(args); err != nil {
+			log.Fatal(err)
+		}
+		return
+	}
+
 	for _, a := range args {
 		if err = RunTask(a); err != nil {
 			log.Fatal(err)