Fix migration order v1.3 (#3157)

* FIx migration order

* Fix migration function file names to match version

* Fix typo

* Add note about ignored errors

* Fix typo, remove wrong comment

models/migrations/v50.go

@@ -0,0 +1,55 @@
+// Copyright 2017 The Gitea Authors. 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 (
+	"time"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/go-xorm/xorm"
+)
+
+func migrateProtectedBranchStruct(x *xorm.Engine) error {
+	type ProtectedBranch struct {
+		ID          int64  `xorm:"pk autoincr"`
+		RepoID      int64  `xorm:"UNIQUE(s)"`
+		BranchName  string `xorm:"UNIQUE(s)"`
+		CanPush     bool
+		Created     time.Time `xorm:"-"`
+		CreatedUnix int64
+		Updated     time.Time `xorm:"-"`
+		UpdatedUnix int64
+	}
+
+	var pbs []ProtectedBranch
+	err := x.Find(&pbs)
+	if err != nil {
+		return err
+	}
+
+	for _, pb := range pbs {
+		if pb.CanPush {
+			if _, err = x.ID(pb.ID).Delete(new(ProtectedBranch)); err != nil {
+				return err
+			}
+		}
+	}
+
+	switch {
+	case setting.UseSQLite3:
+		log.Warn("Unable to drop columns in SQLite")
+	case setting.UseMySQL, setting.UsePostgreSQL, setting.UseMSSQL, setting.UseTiDB:
+		if _, err := x.Exec("ALTER TABLE protected_branch DROP COLUMN can_push"); err != nil {
+			// Ignoring this error in case we run this migration second time (after migration reordering)
+			log.Warn("DROP COLUMN can_push: %v", err)
+		}
+	default:
+		log.Fatal(4, "Unrecognized DB")
+	}
+
+	return nil
+}