include date and dirty flag in version

version.go

@@ -3,31 +3,47 @@ package main
 import (
 	_ "embed"
 	"encoding/json"
+	"fmt"
 	"runtime/debug"
+	"time"
 )
 
-var version string
-
 //go:embed version.json
 var versionJSON []byte
 
-func init() {
+var version = buildVersion()
+
+func buildVersion() string {
 	// Read version from embedded JSON file.
 	var verMap map[string]string
 	json.Unmarshal(versionJSON, &verMap)
-	version = verMap["version"]
+	release := verMap["version"]
 
-	// If running from a module, try to get the build info.
-	bi, ok := debug.ReadBuildInfo()
+	info, ok := debug.ReadBuildInfo()
 	if !ok {
-		return
+		return release + " dev-build"
 	}
 
+	var dirty bool
+	var day, revision string
+
 	// Append the revision to the version.
-	for i := range bi.Settings {
-		if bi.Settings[i].Key == "vcs.revision" {
-			version += "-" + bi.Settings[i].Value
-			break
+	for _, kv := range info.Settings {
+		switch kv.Key {
+		case "vcs.revision":
+			revision = kv.Value[:7]
+		case "vcs.time":
+			t, _ := time.Parse(time.RFC3339, kv.Value)
+			day = t.UTC().Format("2006-01-02")
+		case "vcs.modified":
+			dirty = kv.Value == "true"
 		}
 	}
+	if dirty {
+		revision += "-dirty"
+	}
+	if revision != "" {
+		return fmt.Sprintf("%s %s-%s", release, day, revision)
+	}
+	return release + " dev-build"
 }