Automerge supports deleting branch automatically after merging (#32343)

Resolve #32341 
~Depends on #27151~

- [x] It will display a checkbox of deleting the head branch on the pull
request view page when starting an auto-merge task.
- [x] Add permission check before deleting the branch
- [x] Add delete branch comment for those closing pull requests because
of head branch or base branch was deleted.
- [x] Merge `RetargetChildrenOnMerge` and `AddDeletePRBranchComment`
into `service.DeleteBranch`.

models/issues/pull_list.go

@@ -166,6 +166,23 @@ func (prs PullRequestList) getRepositoryIDs() []int64 {
 	return repoIDs.Values()
 }
 
+func (prs PullRequestList) SetBaseRepo(baseRepo *repo_model.Repository) {
+	for _, pr := range prs {
+		if pr.BaseRepo == nil {
+			pr.BaseRepo = baseRepo
+		}
+	}
+}
+
+func (prs PullRequestList) SetHeadRepo(headRepo *repo_model.Repository) {
+	for _, pr := range prs {
+		if pr.HeadRepo == nil {
+			pr.HeadRepo = headRepo
+			pr.isHeadRepoLoaded = true
+		}
+	}
+}
+
 func (prs PullRequestList) LoadRepositories(ctx context.Context) error {
 	repoIDs := prs.getRepositoryIDs()
 	reposMap := make(map[int64]*repo_model.Repository, len(repoIDs))

models/migrations/migrations.go

@@ -22,6 +22,7 @@ import (
 	"code.gitea.io/gitea/models/migrations/v1_21"
 	"code.gitea.io/gitea/models/migrations/v1_22"
 	"code.gitea.io/gitea/models/migrations/v1_23"
+	"code.gitea.io/gitea/models/migrations/v1_24"
 	"code.gitea.io/gitea/models/migrations/v1_6"
 	"code.gitea.io/gitea/models/migrations/v1_7"
 	"code.gitea.io/gitea/models/migrations/v1_8"
@@ -369,6 +370,9 @@ func prepareMigrationTasks() []*migration {
 		newMigration(309, "Improve Notification table indices", v1_23.ImproveNotificationTableIndices),
 		newMigration(310, "Add Priority to ProtectedBranch", v1_23.AddPriorityToProtectedBranch),
 		newMigration(311, "Add TimeEstimate to Issue table", v1_23.AddTimeEstimateColumnToIssueTable),
+
+		// Gitea 1.23.0-rc0 ends at migration ID number 311 (database version 312)
+		newMigration(312, "Add DeleteBranchAfterMerge to AutoMerge", v1_24.AddDeleteBranchAfterMergeForAutoMerge),
 	}
 	return preparedMigrations
 }

models/migrations/v1_24/v312.go

@@ -0,0 +1,21 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_24 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+type pullAutoMerge struct {
+	DeleteBranchAfterMerge bool
+}
+
+// TableName return database table name for xorm
+func (pullAutoMerge) TableName() string {
+	return "pull_auto_merge"
+}
+
+func AddDeleteBranchAfterMergeForAutoMerge(x *xorm.Engine) error {
+	return x.Sync(new(pullAutoMerge))
+}

models/pull/automerge.go

@@ -15,13 +15,14 @@ import (
 
 // AutoMerge represents a pull request scheduled for merging when checks succeed
 type AutoMerge struct {
-	ID          int64                 `xorm:"pk autoincr"`
-	PullID      int64                 `xorm:"UNIQUE"`
-	DoerID      int64                 `xorm:"INDEX NOT NULL"`
-	Doer        *user_model.User      `xorm:"-"`
-	MergeStyle  repo_model.MergeStyle `xorm:"varchar(30)"`
-	Message     string                `xorm:"LONGTEXT"`
-	CreatedUnix timeutil.TimeStamp    `xorm:"created"`
+	ID                     int64                 `xorm:"pk autoincr"`
+	PullID                 int64                 `xorm:"UNIQUE"`
+	DoerID                 int64                 `xorm:"INDEX NOT NULL"`
+	Doer                   *user_model.User      `xorm:"-"`
+	MergeStyle             repo_model.MergeStyle `xorm:"varchar(30)"`
+	Message                string                `xorm:"LONGTEXT"`
+	DeleteBranchAfterMerge bool
+	CreatedUnix            timeutil.TimeStamp `xorm:"created"`
 }
 
 // TableName return database table name for xorm
@@ -49,7 +50,7 @@ func IsErrAlreadyScheduledToAutoMerge(err error) bool {
 }
 
 // ScheduleAutoMerge schedules a pull request to be merged when all checks succeed
-func ScheduleAutoMerge(ctx context.Context, doer *user_model.User, pullID int64, style repo_model.MergeStyle, message string) error {
+func ScheduleAutoMerge(ctx context.Context, doer *user_model.User, pullID int64, style repo_model.MergeStyle, message string, deleteBranchAfterMerge bool) error {
 	// Check if we already have a merge scheduled for that pull request
 	if exists, _, err := GetScheduledMergeByPullID(ctx, pullID); err != nil {
 		return err
@@ -58,10 +59,11 @@ func ScheduleAutoMerge(ctx context.Context, doer *user_model.User, pullID int64,
 	}
 
 	_, err := db.GetEngine(ctx).Insert(&AutoMerge{
-		DoerID:     doer.ID,
-		PullID:     pullID,
-		MergeStyle: style,
-		Message:    message,
+		DoerID:                 doer.ID,
+		PullID:                 pullID,
+		MergeStyle:             style,
+		Message:                message,
+		DeleteBranchAfterMerge: deleteBranchAfterMerge,
 	})
 	return err
 }