Allow customizable number of expansions

Updates #66

internal/taskfile/taskfile.go

@@ -2,9 +2,10 @@ package taskfile
 
 // Taskfile represents a Taskfile.yml
 type Taskfile struct {
-	Version string
-	Vars    Vars
-	Tasks   Tasks
+	Version    string
+	Expansions int
+	Vars       Vars
+	Tasks      Tasks
 }
 
 // UnmarshalYAML implements yaml.Unmarshaler interface
@@ -15,15 +16,20 @@ func (tf *Taskfile) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	}
 
 	var taskfile struct {
-		Version string
-		Vars    Vars
-		Tasks   Tasks
+		Version    string
+		Expansions int
+		Vars       Vars
+		Tasks      Tasks
 	}
 	if err := unmarshal(&taskfile); err != nil {
 		return err
 	}
 	tf.Version = taskfile.Version
+	tf.Expansions = taskfile.Expansions
 	tf.Vars = taskfile.Vars
 	tf.Tasks = taskfile.Tasks
+	if tf.Expansions <= 0 {
+		tf.Expansions = 2
+	}
 	return nil
 }