Use semver for Taskfile versions

internal/taskfile/taskfile.go

@@ -2,8 +2,7 @@ package taskfile
 
 // Taskfile represents a Taskfile.yml
 type Taskfile struct {
-	// TODO: version is still not used
-	Version int
+	Version string
 	Tasks   Tasks
 }
 
@@ -14,7 +13,7 @@ func (tf *Taskfile) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	}
 
 	var taskfile struct {
-		Version int
+		Version string
 		Tasks   Tasks
 	}
 	if err := unmarshal(&taskfile); err != nil {

internal/taskfile/version/version.go

@@ -0,0 +1,45 @@
+package version
+
+import (
+	"github.com/Masterminds/semver"
+)
+
+var (
+	v1 = mustVersion("1")
+	v2 = mustVersion("2")
+
+	isV1  = mustConstraint("= 1")
+	isV2  = mustConstraint(">= 2")
+	isV21 = mustConstraint(">= 2.1")
+)
+
+// IsV1 returns if is a given Taskfile version is version 1
+func IsV1(v *semver.Version) bool {
+	return isV1.Check(v)
+}
+
+// IsV2 returns if is a given Taskfile version is at least version 2
+func IsV2(v *semver.Version) bool {
+	return isV2.Check(v)
+}
+
+// IsV21 returns if is a given Taskfile version is at least version 2
+func IsV21(v *semver.Version) bool {
+	return isV21.Check(v)
+}
+
+func mustVersion(s string) *semver.Version {
+	v, err := semver.NewVersion(s)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func mustConstraint(s string) *semver.Constraints {
+	c, err := semver.NewConstraint(s)
+	if err != nil {
+		panic(err)
+	}
+	return c
+}