Sync branches into databases (#22743)

Related #14180
Related #25233 
Related #22639
Close #19786
Related #12763 

This PR will change all the branches retrieve method from reading git
data to read database to reduce git read operations.

- [x] Sync git branches information into database when push git data
- [x] Create a new table `Branch`, merge some columns of `DeletedBranch`
into `Branch` table and drop the table `DeletedBranch`.
- [x] Read `Branch` table when visit `code` -> `branch` page
- [x] Read `Branch` table when list branch names in `code` page dropdown
- [x] Read `Branch` table when list git ref compare page
- [x] Provide a button in admin page to manually sync all branches.
- [x] Sync branches if repository is not empty but database branches are
empty when visiting pages with branches list
- [x] Use `commit_time desc` as the default FindBranch order by to keep
consistent as before and deleted branches will be always at the end.

---------

Co-authored-by: Jason Song <i@wolfogre.com>

models/migrations/v1_21/v264.go

@@ -0,0 +1,93 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_21 //nolint
+
+import (
+	"context"
+	"fmt"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func AddBranchTable(x *xorm.Engine) error {
+	type Branch struct {
+		ID            int64
+		RepoID        int64  `xorm:"UNIQUE(s)"`
+		Name          string `xorm:"UNIQUE(s) NOT NULL"`
+		CommitID      string
+		CommitMessage string `xorm:"TEXT"`
+		PusherID      int64
+		IsDeleted     bool `xorm:"index"`
+		DeletedByID   int64
+		DeletedUnix   timeutil.TimeStamp `xorm:"index"`
+		CommitTime    timeutil.TimeStamp // The commit
+		CreatedUnix   timeutil.TimeStamp `xorm:"created"`
+		UpdatedUnix   timeutil.TimeStamp `xorm:"updated"`
+	}
+
+	if err := x.Sync(new(Branch)); err != nil {
+		return err
+	}
+
+	if exist, err := x.IsTableExist("deleted_branches"); err != nil {
+		return err
+	} else if !exist {
+		return nil
+	}
+
+	type DeletedBranch struct {
+		ID          int64
+		RepoID      int64  `xorm:"index UNIQUE(s)"`
+		Name        string `xorm:"UNIQUE(s) NOT NULL"`
+		Commit      string
+		DeletedByID int64
+		DeletedUnix timeutil.TimeStamp
+	}
+
+	var adminUserID int64
+	has, err := x.Table("user").
+		Select("id").
+		Where("is_admin=?", true).
+		Asc("id"). // Reliably get the admin with the lowest ID.
+		Get(&adminUserID)
+	if err != nil {
+		return err
+	} else if !has {
+		return fmt.Errorf("no admin user found")
+	}
+
+	branches := make([]Branch, 0, 100)
+	if err := db.Iterate(context.Background(), nil, func(ctx context.Context, deletedBranch *DeletedBranch) error {
+		branches = append(branches, Branch{
+			RepoID:      deletedBranch.RepoID,
+			Name:        deletedBranch.Name,
+			CommitID:    deletedBranch.Commit,
+			PusherID:    adminUserID,
+			IsDeleted:   true,
+			DeletedByID: deletedBranch.DeletedByID,
+			DeletedUnix: deletedBranch.DeletedUnix,
+		})
+		if len(branches) >= 100 {
+			_, err := x.Insert(&branches)
+			if err != nil {
+				return err
+			}
+			branches = branches[:0]
+		}
+		return nil
+	}); err != nil {
+		return err
+	}
+
+	if len(branches) > 0 {
+		if _, err := x.Insert(&branches); err != nil {
+			return err
+		}
+	}
+
+	return x.DropTables("deleted_branches")
+}