Provide Version from injected var if available

Makefile

@@ -1,5 +1,7 @@
+VERSION=$(shell git describe --tags)
+
 build:
-	go build
+	go build -ldflags="-X main.Version=$(VERSION)"
 
 test:
 	go test

version.go

@@ -6,18 +6,21 @@ import (
 	"runtime/debug"
 )
 
-const AppVersion = "v0.2.0"
+var Version string
 
 type versionCmd struct{}
 
 func (cmd *versionCmd) run(args []string) error {
 	// TODO: Use Settings.VCS.Version from Go v1.18
-	version := "devel"
-	info, ok := debug.ReadBuildInfo()
-	if ok {
-		version = info.Main.Version
+	if Version == "" {
+		info, ok := debug.ReadBuildInfo()
+		if ok {
+			Version = info.Main.Version
+		} else {
+			Version = "devel"
+		}
 	}
-	fmt.Println("hkt version", version)
+	fmt.Println("hkt version", Version)
 	return nil
 }