feat: fall back to runtime/debug.ReadBuildInfo for version info

When ldflags are not set (e.g., via go install), read VCS metadata
embedded by the Go toolchain so users get meaningful version output
instead of "dev (none) built unknown".

Author: debidong

cmd/flashduty/main.go

@@ -3,20 +3,57 @@ package main
 import (
 	"fmt"
 	"os"
+	"runtime/debug"
 
 	"github.com/flashcatcloud/flashduty-cli/internal/cli"
 )
 
 var (
-	version = "dev"
-	commit  = "none"
-	date    = "unknown"
+	version = ""
+	commit  = ""
+	date    = ""
 )
 
 func main() {
+	if version == "" {
+		readBuildInfo()
+	}
+	if version == "" {
+		version = "dev"
+	}
+	if commit == "" {
+		commit = "none"
+	}
+	if date == "" {
+		date = "unknown"
+	}
 	cli.SetVersionInfo(version, commit, date)
 	if err := cli.Execute(); err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %s\n", err)
 		os.Exit(1)
 	}
 }
+
+func readBuildInfo() {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+	version = info.Main.Version
+	for _, s := range info.Settings {
+		switch s.Key {
+		case "vcs.revision":
+			if len(s.Value) > 7 {
+				commit = s.Value[:7]
+			} else {
+				commit = s.Value
+			}
+		case "vcs.time":
+			date = s.Value
+		case "vcs.modified":
+			if s.Value == "true" {
+				version += "-dirty"
+			}
+		}
+	}
+}