Don't rewrite non-gitea public keys (#906)

* don't rewrite non-gitea public keys

* add comment for public key

models/migrations/v21.go

@@ -0,0 +1,53 @@
+// Copyright 2017 Gitea. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/go-xorm/xorm"
+)
+
+const (
+	tplCommentPrefix = `# gitea public key`
+	tplPublicKey     = tplCommentPrefix + "\n" + `command="%s serv key-%d --config='%s'",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty %s` + "\n"
+)
+
+func useNewPublickeyFormat(x *xorm.Engine) error {
+	fpath := filepath.Join(setting.SSH.RootPath, "authorized_keys")
+	tmpPath := fpath + ".tmp"
+	f, err := os.OpenFile(tmpPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		f.Close()
+		os.Remove(tmpPath)
+	}()
+
+	type PublicKey struct {
+		ID      int64
+		Content string
+	}
+
+	err = x.Iterate(new(PublicKey), func(idx int, bean interface{}) (err error) {
+		key := bean.(*PublicKey)
+		_, err = f.WriteString(fmt.Sprintf(tplPublicKey, setting.AppPath, key.ID, setting.CustomConf, key.Content))
+		return err
+	})
+	if err != nil {
+		return err
+	}
+
+	f.Close()
+	if err = os.Rename(tmpPath, fpath); err != nil {
+		return err
+	}
+	return nil
+}