feat(dltl): add header to downladed schema

_schema/telegram.tl

@@ -1,3 +1,9 @@
+// Code generated by ./cmd/dltl, DO NOT EDIT.
+//
+// Source: https://raw.githubusercontent.com/telegramdesktop/tdesktop/dev/Telegram/Resources/tl/api.tl
+// Layer:  122
+// SHA256: 4b2e953d778fb0bf3f3cdd4c659396cc247df949a3d01dca916948909196a1ef
+
 boolFalse#bc799737 = Bool;
 
 boolTrue#997275b5 = Bool;

cmd/dltl/main.go

@@ -2,13 +2,15 @@
 package main
 
 import (
+	"crypto/sha256"
 	"flag"
 	"fmt"
 	"io"
 	"net/http"
 	"net/url"
 	"os"
 	"path"
+	"strings"
 
 	"github.com/gotd/tl"
 )
@@ -40,7 +42,8 @@ func main() {
 	}
 
 	// Parsing in-place.
-	s, err := tl.Parse(res.Body)
+	h := sha256.New()
+	s, err := tl.Parse(io.TeeReader(res.Body, h))
 	if err != nil {
 		panic(err)
 	}
@@ -59,6 +62,20 @@ func main() {
 		outWriter = w
 	}
 
+	// Writing header to avoid manual edit.
+	var b strings.Builder
+	b.WriteString("// Code generated by ./cmd/dltl, DO NOT EDIT.\n")
+	b.WriteString("//\n")
+	b.WriteString(fmt.Sprintf("// Source: %s\n", u))
+	if s.Layer > 0 {
+		b.WriteString(fmt.Sprintf("// Layer:  %d\n", s.Layer))
+	}
+	b.WriteString(fmt.Sprintf("// SHA256: %x\n", h.Sum(nil)))
+	b.WriteRune('\n')
+	if _, err := io.WriteString(outWriter, b.String()); err != nil {
+		panic(err)
+	}
+
 	if _, err := s.WriteTo(outWriter); err != nil {
 		panic(err)
 	}