Move to setting version info explicitly in linker flags

We don't have go built-in VCS information in a nix build because the git
repository isn't present. After struggling to build an overlay that
would provide it, I decided this path is easier of just injecting in the
data that we need.

Issue: #5

main.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/signal"
 	"runtime/debug"
+	//"strconv"
 	"syscall"
 	"time"
 
@@ -33,6 +34,13 @@ import (
 	"source.gleipnir.technology/Gleipnir/nidus-sync/version"
 )
 
+// These will be set by ldflags at build time by Nix
+var (
+	BuildTime = "unknown"
+	Revision  = "unknown"
+	Version   = "dev"
+)
+
 func main() {
 	err := config.Parse()
 	if err != nil {
@@ -46,8 +54,19 @@ func main() {
 		log.Warn().Msg("Forcing production mode for testing templates")
 		config.Environment = "PRODUCTION"
 	}
-	v := version.Get()
-	log.Info().Str("environment", config.Environment).Bool("is-prod", config.IsProductionEnvironment()).Str("revision", v.Revision).Str("build_time", v.BuildTime.String()).Bool("is modified", v.IsModified).Msg("Starting")
+	v := GetVersionInfo()
+	log.Info().
+		Str("environment", config.Environment).
+		Bool("is-prod", config.IsProductionEnvironment()).
+		Str("revision", v.Revision).
+		Str("build_time", v.BuildTime.String()).
+		Bool("is modified", v.IsModified).
+		Str("Version", Version).
+		Str("Revision", Revision).
+		Str("BuildDate", BuildTime).
+		Msg("Starting")
+	api.SetVersionInfo(v)
+
 	err = sentry.Init(sentry.ClientOptions{
 		Debug:            false, //!config.IsProductionEnvironment(),
 		Dsn:              config.SentryDSN,
@@ -285,3 +304,50 @@ func LoggerMiddleware(logger *zerolog.Logger) func(next http.Handler) http.Handl
 		return http.HandlerFunc(fn)
 	}
 }
+func GetVersionInfo() (version.VersionInfo, error) {
+	// Try ldflags first (set by Nix build)
+	if Revision != "" && Revision != "unknown" {
+		build_time, err := parseNixTime(BuildTime)
+		if err != nil {
+			return version.VersionInfo{}, fmt.Errorf("parse nix time: %w", err)
+		}
+		return version.VersionInfo{
+			BuildTime:  build_time,
+			IsModified: Revision == "dirty",
+			Revision:   Revision,
+		}, nil
+	}
+
+	// Fallback to debug.ReadBuildInfo() for development
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return version.VersionInfo{}, fmt.Errorf("read build info not ok")
+	}
+
+	var v version.VersionInfo
+	for _, setting := range info.Settings {
+		switch setting.Key {
+		case "vcs.modified":
+			v.IsModified = setting.Value == "true"
+		case "vcs.revision":
+			if len(setting.Value) > 7 {
+				v.Revision = setting.Value[:7]
+			} else {
+				v.Revision = setting.Value
+			}
+		case "vcs.time":
+			if t, err := time.Parse(time.RFC3339, setting.Value); err == nil {
+				v.BuildTime = t
+			}
+		}
+	}
+	return v, nil
+}
+func parseNixTime(timestamp string) (time.Time, error) {
+	layout := "20060102150405"
+	t, err := time.Parse(layout, timestamp)
+	if err != nil {
+		return time.Time{}, err
+	}
+	return t, nil
+}