internal/witcli: add Version helper

internal/witcli/version.go

@@ -0,0 +1,34 @@
+package witcli
+
+import (
+	"runtime/debug"
+	"sync"
+)
+
+// Version returns the version string of this module.
+func Version() string {
+	return versionString()
+}
+
+var versionString = sync.OnceValue(func() string {
+	build, ok := debug.ReadBuildInfo()
+	if !ok {
+		return "(none)"
+	}
+	version := build.Main.Version
+	var revision string
+	for _, s := range build.Settings {
+		switch s.Key {
+		case "vcs.revision":
+			revision = s.Value
+		}
+	}
+	if version == "" {
+		version = "(none)"
+	}
+	versionString := version
+	if revision != "" {
+		versionString += " (" + revision + ")"
+	}
+	return versionString
+})