Auto merge pull requests when all checks succeeded via API (#9307)

* Fix indention

Signed-off-by: kolaente <k@knt.li>

* Add option to merge a pr right now without waiting for the checks to succeed

Signed-off-by: kolaente <k@knt.li>

* Fix lint

Signed-off-by: kolaente <k@knt.li>

* Add scheduled pr merge to tables used for testing

Signed-off-by: kolaente <k@knt.li>

* Add status param to make GetPullRequestByHeadBranch reusable

Signed-off-by: kolaente <k@knt.li>

* Move "Merge now" to a seperate button to make the ui clearer

Signed-off-by: kolaente <k@knt.li>

* Update models/scheduled_pull_request_merge.go

Co-authored-by: 赵智超 <1012112796@qq.com>

* Update web_src/js/index.js

Co-authored-by: 赵智超 <1012112796@qq.com>

* Update web_src/js/index.js

Co-authored-by: 赵智超 <1012112796@qq.com>

* Re-add migration after merge

* Fix frontend lint

* Fix version compare

* Add vendored dependencies

* Add basic tets

* Make sure the api route is capable of scheduling PRs for merging

* Fix comparing version

* make vendor

* adopt refactor

* apply suggestion: User -> Doer

* init var once

* Fix Test

* Update templates/repo/issue/view_content/comments.tmpl

* adopt

* nits

* next

* code format

* lint

* use same name schema; rm CreateUnScheduledPRToAutoMergeComment

* API: can not create schedule twice

* Add TestGetBranchNamesForSha

* nits

* new go routine for each pull to merge

* Update models/pull.go

Co-authored-by: a1012112796 <1012112796@qq.com>

* Update models/scheduled_pull_request_merge.go

Co-authored-by: a1012112796 <1012112796@qq.com>

* fix & add renaming sugestions

* Update services/automerge/pull_auto_merge.go

Co-authored-by: a1012112796 <1012112796@qq.com>

* fix conflict relicts

* apply latest refactors

* fix: migration after merge

* Update models/error.go

Co-authored-by: delvh <dev.lh@web.de>

* Update options/locale/locale_en-US.ini

Co-authored-by: delvh <dev.lh@web.de>

* Update options/locale/locale_en-US.ini

Co-authored-by: delvh <dev.lh@web.de>

* adapt latest refactors

* fix test

* use more context

* skip potential edgecases

* document func usage

* GetBranchNamesForSha() -> GetRefsBySha()

* start refactoring

* ajust to new changes

* nit

* docu nit

* the great check move

* move checks for branchprotection into own package

* resolve todo now ...

* move & rename

* unexport if posible

* fix

* check if merge is allowed before merge on scheduled pull

* debugg

* wording

* improve SetDefaults & nits

* NotAllowedToMerge -> DisallowedToMerge

* fix test

* merge files

* use package "errors"

* merge files

* add string names

* other implementation for gogit

* adapt refactor

* more context for models/pull.go

* GetUserRepoPermission use context

* more ctx

* use context for loading pull head/base-repo

* more ctx

* more ctx

* models.LoadIssueCtx()

* models.LoadIssueCtx()

* Handle pull_service.Merge in one DB transaction

* add TODOs

* next

* next

* next

* more ctx

* more ctx

* Start refactoring structure of old pull code ...

* move code into new packages

* shorter names ... and finish **restructure**

* Update models/branches.go

Co-authored-by: zeripath <art27@cantab.net>

* finish UpdateProtectBranch

* more and fix

* update datum

* template: use "svg" helper

* rename prQueue 2 prPatchCheckerQueue

* handle automerge in queue

* lock pull on git&db actions ...

* lock pull on git&db actions ...

* add TODO notes

* the regex

* transaction in tests

* GetRepositoryByIDCtx

* shorter table name and lint fix

* close transaction bevore notify

* Update models/pull.go

* next

* CheckPullMergable check all branch protections!

* Update routers/web/repo/pull.go

* CheckPullMergable check all branch protections!

* Revert "PullService lock via pullID (#19520)" (for now...)

This reverts commit 6cde7c9159a5ea75a10356feb7b8c7ad4c434a9a.

* Update services/pull/check.go

* Use for a repo action one database transaction

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: delvh <dev.lh@web.de>

* Update services/issue/status.go

Co-authored-by: delvh <dev.lh@web.de>

* Update services/issue/status.go

Co-authored-by: delvh <dev.lh@web.de>

* use db.WithTx()

* gofmt

* make pr.GetDefaultMergeMessage() context aware

* make MergePullRequestForm.SetDefaults context aware

* use db.WithTx()

* pull.SetMerged only with context

* fix deadlock in `test-sqlite\#TestAPIBranchProtection`

* dont forget templates

* db.WithTx allow to set the parentCtx

* handle db transaction in service packages but not router

* issue_service.ChangeStatus just had caused another deadlock :/
it has to do something with how notification package is handled

* if we merge a pull in one database transaktion, we get a lock, because merge infoce internal api that cant handle open db sessions to the same repo

* ajust to current master

* Apply suggestions from code review

Co-authored-by: delvh <dev.lh@web.de>

* dont open db transaction in router

* make generate-swagger

* one _success less

* wording nit

* rm

* adapt

* remove not needed test files

* rm less diff & use attr in JS

* ...

* Update services/repository/files/commit.go

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* ajust db schema for PullAutoMerge

* skip broken pull refs

* more context in error messages

* remove webUI part for another pull

* remove more WebUI only parts

* API: add CancleAutoMergePR

* Apply suggestions from code review

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* fix lint

* Apply suggestions from code review

* cancle -> cancel

Co-authored-by: delvh <dev.lh@web.de>

* change queue identifyer

* fix swagger

* prevent nil issue

* fix and dont drop error

* as per @zeripath

* Update integrations/git_test.go

Co-authored-by: delvh <dev.lh@web.de>

* Update integrations/git_test.go

Co-authored-by: delvh <dev.lh@web.de>

* more declarative integration tests (dedup code)

* use assert.False/True helper

Co-authored-by: 赵智超 <1012112796@qq.com>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

integrations/api_helper_for_declarative_test.go

@@ -314,6 +314,37 @@ func doAPIManuallyMergePullRequest(ctx APITestContext, owner, repo, commitID str
 	}
 }
 
+func doAPIAutoMergePullRequest(ctx APITestContext, owner, repo string, index int64) func(*testing.T) {
+	return func(t *testing.T) {
+		urlStr := fmt.Sprintf("/api/v1/repos/%s/%s/pulls/%d/merge?token=%s",
+			owner, repo, index, ctx.Token)
+		req := NewRequestWithJSON(t, http.MethodPost, urlStr, &forms.MergePullRequestForm{
+			MergeMessageField:      "doAPIMergePullRequest Merge",
+			Do:                     string(repo_model.MergeStyleMerge),
+			MergeWhenChecksSucceed: true,
+		})
+
+		if ctx.ExpectedCode != 0 {
+			ctx.Session.MakeRequest(t, req, ctx.ExpectedCode)
+			return
+		}
+		ctx.Session.MakeRequest(t, req, 200)
+	}
+}
+
+func doAPICancelAutoMergePullRequest(ctx APITestContext, owner, repo string, index int64) func(*testing.T) {
+	return func(t *testing.T) {
+		urlStr := fmt.Sprintf("/api/v1/repos/%s/%s/pulls/%d/merge?token=%s",
+			owner, repo, index, ctx.Token)
+		req := NewRequest(t, http.MethodDelete, urlStr)
+		if ctx.ExpectedCode != 0 {
+			ctx.Session.MakeRequest(t, req, ctx.ExpectedCode)
+			return
+		}
+		ctx.Session.MakeRequest(t, req, 204)
+	}
+}
+
 func doAPIGetBranch(ctx APITestContext, branch string, callback ...func(*testing.T, api.Branch)) func(*testing.T) {
 	return func(t *testing.T) {
 		req := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/branches/%s?token=%s", ctx.Username, ctx.Reponame, branch, ctx.Token)

integrations/git_test.go

@@ -82,6 +82,7 @@ func testGit(t *testing.T, u *url.URL) {
 
 		t.Run("CreateAgitFlowPull", doCreateAgitFlowPull(dstPath, &httpContext, "master", "test/head"))
 		t.Run("BranchProtectMerge", doBranchProtectPRMerge(&httpContext, dstPath))
+		t.Run("AutoMerge", doAutoPRMerge(&httpContext, dstPath))
 		t.Run("CreatePRAndSetManuallyMerged", doCreatePRAndSetManuallyMerged(httpContext, httpContext, dstPath, "master", "test-manually-merge"))
 		t.Run("MergeFork", func(t *testing.T) {
 			defer PrintCurrentTest(t)()
@@ -615,6 +616,88 @@ func doBranchDelete(ctx APITestContext, owner, repo, branch string) func(*testin
 	}
 }
 
+func doAutoPRMerge(baseCtx *APITestContext, dstPath string) func(t *testing.T) {
+	return func(t *testing.T) {
+		defer PrintCurrentTest(t)()
+
+		ctx := NewAPITestContext(t, baseCtx.Username, baseCtx.Reponame)
+
+		t.Run("CheckoutProtected", doGitCheckoutBranch(dstPath, "protected"))
+		t.Run("PullProtected", doGitPull(dstPath, "origin", "protected"))
+		t.Run("GenerateCommit", func(t *testing.T) {
+			_, err := generateCommitWithNewData(littleSize, dstPath, "user2@example.com", "User Two", "branch-data-file-")
+			assert.NoError(t, err)
+		})
+		t.Run("PushToUnprotectedBranch", doGitPushTestRepository(dstPath, "origin", "protected:unprotected3"))
+		var pr api.PullRequest
+		var err error
+		t.Run("CreatePullRequest", func(t *testing.T) {
+			pr, err = doAPICreatePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, "protected", "unprotected3")(t)
+			assert.NoError(t, err)
+		})
+
+		// Request repository commits page
+		req := NewRequest(t, "GET", fmt.Sprintf("/%s/%s/pulls/%d/commits", baseCtx.Username, baseCtx.Reponame, pr.Index))
+		resp := ctx.Session.MakeRequest(t, req, http.StatusOK)
+		doc := NewHTMLParser(t, resp.Body)
+
+		// Get first commit URL
+		commitURL, exists := doc.doc.Find("#commits-table tbody tr td.sha a").Last().Attr("href")
+		assert.True(t, exists)
+		assert.NotEmpty(t, commitURL)
+
+		commitID := path.Base(commitURL)
+
+		// Call API to add Pending status for commit
+		t.Run("CreateStatus", doAPICreateCommitStatus(ctx, commitID, api.CommitStatusPending))
+
+		// Cancel not existing auto merge
+		ctx.ExpectedCode = http.StatusNotFound
+		t.Run("CancelAutoMergePR", doAPICancelAutoMergePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index))
+
+		// Add auto merge request
+		ctx.ExpectedCode = http.StatusCreated
+		t.Run("AutoMergePR", doAPIAutoMergePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index))
+
+		// Can not create schedule twice
+		ctx.ExpectedCode = http.StatusConflict
+		t.Run("AutoMergePRTwice", doAPIAutoMergePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index))
+
+		// Cancel auto merge request
+		ctx.ExpectedCode = http.StatusNoContent
+		t.Run("CancelAutoMergePR", doAPICancelAutoMergePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index))
+
+		// Add auto merge request
+		ctx.ExpectedCode = http.StatusCreated
+		t.Run("AutoMergePR", doAPIAutoMergePullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index))
+
+		// Check pr status
+		ctx.ExpectedCode = 0
+		pr, err = doAPIGetPullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index)(t)
+		assert.NoError(t, err)
+		assert.False(t, pr.HasMerged)
+
+		// Call API to add Failure status for commit
+		t.Run("CreateStatus", doAPICreateCommitStatus(ctx, commitID, api.CommitStatusFailure))
+
+		// Check pr status
+		pr, err = doAPIGetPullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index)(t)
+		assert.NoError(t, err)
+		assert.False(t, pr.HasMerged)
+
+		// Call API to add Success status for commit
+		t.Run("CreateStatus", doAPICreateCommitStatus(ctx, commitID, api.CommitStatusSuccess))
+
+		// wait to let gitea merge stuff
+		time.Sleep(time.Second)
+
+		// test pr status
+		pr, err = doAPIGetPullRequest(ctx, baseCtx.Username, baseCtx.Reponame, pr.Index)(t)
+		assert.NoError(t, err)
+		assert.True(t, pr.HasMerged)
+	}
+}
+
 func doCreateAgitFlowPull(dstPath string, ctx *APITestContext, baseBranch, headBranch string) func(t *testing.T) {
 	return func(t *testing.T) {
 		defer PrintCurrentTest(t)()

integrations/pull_status_test.go

@@ -63,20 +63,13 @@ func TestPullCreate_CommitStatus(t *testing.T) {
 			api.CommitStatusWarning: "warning sign icon yellow",
 		}
 
+		testCtx := NewAPITestContext(t, "user1", "repo1")
+
 		// Update commit status, and check if icon is updated as well
 		for _, status := range statusList {
 
 			// Call API to add status for commit
-			token := getTokenForLoggedInUser(t, session)
+			t.Run("CreateStatus", doAPICreateCommitStatus(testCtx, commitID, status))
-			req = NewRequestWithJSON(t, "POST", fmt.Sprintf("/api/v1/repos/user1/repo1/statuses/%s?token=%s", commitID, token),
-				api.CreateStatusOption{
-					State:       status,
-					TargetURL:   "http://test.ci/",
-					Description: "",
-					Context:     "testci",
-				},
-			)
-			session.MakeRequest(t, req, http.StatusCreated)
 
 			req = NewRequestf(t, "GET", "/user1/repo1/pulls/1/commits")
 			resp = session.MakeRequest(t, req, http.StatusOK)
@@ -94,6 +87,24 @@ func TestPullCreate_CommitStatus(t *testing.T) {
 	})
 }
 
+func doAPICreateCommitStatus(ctx APITestContext, commitID string, status api.CommitStatusState) func(*testing.T) {
+	return func(t *testing.T) {
+		req := NewRequestWithJSON(t, http.MethodPost, fmt.Sprintf("/api/v1/repos/%s/%s/statuses/%s?token=%s", ctx.Username, ctx.Reponame, commitID, ctx.Token),
+			api.CreateStatusOption{
+				State:       status,
+				TargetURL:   "http://test.ci/",
+				Description: "",
+				Context:     "testci",
+			},
+		)
+		if ctx.ExpectedCode != 0 {
+			ctx.Session.MakeRequest(t, req, ctx.ExpectedCode)
+			return
+		}
+		ctx.Session.MakeRequest(t, req, http.StatusCreated)
+	}
+}
+
 func TestPullCreate_EmptyChangesWithCommits(t *testing.T) {
 	onGiteaRun(t, func(t *testing.T, u *url.URL) {
 		session := loginUser(t, "user1")

integrations/repo_commits_test.go

@@ -36,7 +36,6 @@ func doTestRepoCommitWithStatus(t *testing.T, state string, classes ...string) {
 	defer prepareTestEnv(t)()
 
 	session := loginUser(t, "user2")
-	token := getTokenForLoggedInUser(t, session)
 
 	// Request repository commits page
 	req := NewRequest(t, "GET", "/user2/repo1/commits/branch/master")
@@ -49,16 +48,7 @@ func doTestRepoCommitWithStatus(t *testing.T, state string, classes ...string) {
 	assert.NotEmpty(t, commitURL)
 
 	// Call API to add status for commit
-	req = NewRequestWithJSON(t, "POST", "/api/v1/repos/user2/repo1/statuses/"+path.Base(commitURL)+"?token="+token,
+	t.Run("CreateStatus", doAPICreateCommitStatus(NewAPITestContext(t, "user2", "repo1"), path.Base(commitURL), api.CommitStatusState(state)))
-		api.CreateStatusOption{
-			State:       api.CommitStatusState(state),
-			TargetURL:   "http://test.ci/",
-			Description: "",
-			Context:     "testci",
-		},
-	)
-
-	resp = session.MakeRequest(t, req, http.StatusCreated)
 
 	req = NewRequest(t, "GET", "/user2/repo1/commits/branch/master")
 	resp = session.MakeRequest(t, req, http.StatusOK)

models/issue_comment.go

@@ -110,6 +110,10 @@ const (
 	CommentTypeDismissReview
 	// 33 Change issue ref
 	CommentTypeChangeIssueRef
+	// 34 pr was scheduled to auto merge when checks succeed
+	CommentTypePRScheduledToAutoMerge
+	// 35 pr was un scheduled to auto merge when checks succeed
+	CommentTypePRUnScheduledToAutoMerge
 )
 
 var commentStrings = []string{
@@ -147,6 +151,8 @@ var commentStrings = []string{
 	"project_board",
 	"dismiss_review",
 	"change_issue_ref",
+	"pull_scheduled_merge",
+	"pull_cancel_scheduled_merge",
 }
 
 func (t CommentType) String() string {

models/migrations/migrations.go

@@ -383,6 +383,8 @@ var migrations = []Migration{
 	NewMigration("Add package tables", addPackageTables),
 	// v213 -> v214
 	NewMigration("Add allow edits from maintainers to PullRequest table", addAllowMaintainerEdit),
+	// v214 -> v215
+	NewMigration("Add auto merge table", addAutoMergeTable),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v214.go

@@ -0,0 +1,23 @@
+// Copyright 2022 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 (
+	"xorm.io/xorm"
+)
+
+func addAutoMergeTable(x *xorm.Engine) error {
+	type MergeStyle string
+	type PullAutoMerge struct {
+		ID          int64      `xorm:"pk autoincr"`
+		PullID      int64      `xorm:"UNIQUE"`
+		DoerID      int64      `xorm:"NOT NULL"`
+		MergeStyle  MergeStyle `xorm:"varchar(30)"`
+		Message     string     `xorm:"LONGTEXT"`
+		CreatedUnix int64      `xorm:"created"`
+	}
+
+	return x.Sync2(&PullAutoMerge{})
+}

models/pull.go

@@ -20,6 +20,8 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
+
+	"xorm.io/builder"
 )
 
 // PullRequestType defines pull request type
@@ -675,6 +677,18 @@ func (pr *PullRequest) IsSameRepo() bool {
 	return pr.BaseRepoID == pr.HeadRepoID
 }
 
+// GetPullRequestsByHeadBranch returns all prs by head branch
+// Since there could be multiple prs with the same head branch, this function returns a slice of prs
+func GetPullRequestsByHeadBranch(ctx context.Context, headBranch string, headRepoID int64) ([]*PullRequest, error) {
+	log.Trace("GetPullRequestsByHeadBranch: headBranch: '%s', headRepoID: '%d'", headBranch, headRepoID)
+	prs := make([]*PullRequest, 0, 2)
+	if err := db.GetEngine(ctx).Where(builder.Eq{"head_branch": headBranch, "head_repo_id": headRepoID}).
+		Find(&prs); err != nil {
+		return nil, err
+	}
+	return prs, nil
+}
+
 // GetBaseBranchHTMLURL returns the HTML URL of the base branch
 func (pr *PullRequest) GetBaseBranchHTMLURL() string {
 	if err := pr.LoadBaseRepo(); err != nil {

models/pull/automerge.go

@@ -0,0 +1,143 @@
+// Copyright 2022 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 pull
+
+import (
+	"context"
+	"fmt"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/models/db"
+	repo_model "code.gitea.io/gitea/models/repo"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/timeutil"
+)
+
+// 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:"NOT NULL"`
+	Doer        *user_model.User      `xorm:"-"`
+	MergeStyle  repo_model.MergeStyle `xorm:"varchar(30)"`
+	Message     string                `xorm:"LONGTEXT"`
+	CreatedUnix timeutil.TimeStamp    `xorm:"created"`
+}
+
+// TableName return database table name for xorm
+func (AutoMerge) TableName() string {
+	return "pull_auto_merge"
+}
+
+func init() {
+	db.RegisterModel(new(AutoMerge))
+}
+
+// ErrAlreadyScheduledToAutoMerge represents a "PullRequestHasMerged"-error
+type ErrAlreadyScheduledToAutoMerge struct {
+	PullID int64
+}
+
+func (err ErrAlreadyScheduledToAutoMerge) Error() string {
+	return fmt.Sprintf("pull request is already scheduled to auto merge when checks succeed [pull_id: %d]", err.PullID)
+}
+
+// IsErrAlreadyScheduledToAutoMerge checks if an error is a ErrAlreadyScheduledToAutoMerge.
+func IsErrAlreadyScheduledToAutoMerge(err error) bool {
+	_, ok := err.(ErrAlreadyScheduledToAutoMerge)
+	return ok
+}
+
+// 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 {
+	// Check if we already have a merge scheduled for that pull request
+	if exists, _, err := GetScheduledMergeByPullID(ctx, pullID); err != nil {
+		return err
+	} else if exists {
+		return ErrAlreadyScheduledToAutoMerge{PullID: pullID}
+	}
+
+	if _, err := db.GetEngine(ctx).Insert(&AutoMerge{
+		DoerID:     doer.ID,
+		PullID:     pullID,
+		MergeStyle: style,
+		Message:    message,
+	}); err != nil {
+		return err
+	}
+
+	pr, err := models.GetPullRequestByID(ctx, pullID)
+	if err != nil {
+		return err
+	}
+
+	_, err = createAutoMergeComment(ctx, models.CommentTypePRScheduledToAutoMerge, pr, doer)
+	return err
+}
+
+// GetScheduledMergeByPullID gets a scheduled pull request merge by pull request id
+func GetScheduledMergeByPullID(ctx context.Context, pullID int64) (bool, *AutoMerge, error) {
+	scheduledPRM := &AutoMerge{}
+	exists, err := db.GetEngine(ctx).Where("pull_id = ?", pullID).Get(scheduledPRM)
+	if err != nil || !exists {
+		return false, nil, err
+	}
+
+	doer, err := user_model.GetUserByIDCtx(ctx, scheduledPRM.DoerID)
+	if err != nil {
+		return false, nil, err
+	}
+
+	scheduledPRM.Doer = doer
+	return true, scheduledPRM, nil
+}
+
+// RemoveScheduledAutoMerge cancels a previously scheduled pull request
+func RemoveScheduledAutoMerge(ctx context.Context, doer *user_model.User, pullID int64, comment bool) error {
+	return db.WithTx(func(ctx context.Context) error {
+		exist, scheduledPRM, err := GetScheduledMergeByPullID(ctx, pullID)
+		if err != nil {
+			return err
+		} else if !exist {
+			return models.ErrNotExist{ID: pullID}
+		}
+
+		if _, err := db.GetEngine(ctx).ID(scheduledPRM.ID).Delete(&AutoMerge{}); err != nil {
+			return err
+		}
+
+		// if pull got merged we don't need to add "auto-merge canceled comment"
+		if !comment || doer == nil {
+			return nil
+		}
+
+		pr, err := models.GetPullRequestByID(ctx, pullID)
+		if err != nil {
+			return err
+		}
+
+		_, err = createAutoMergeComment(ctx, models.CommentTypePRUnScheduledToAutoMerge, pr, doer)
+		return err
+	}, ctx)
+}
+
+// createAutoMergeComment is a internal function, only use it for CommentTypePRScheduledToAutoMerge and CommentTypePRUnScheduledToAutoMerge CommentTypes
+func createAutoMergeComment(ctx context.Context, typ models.CommentType, pr *models.PullRequest, doer *user_model.User) (comment *models.Comment, err error) {
+	if err = pr.LoadIssueCtx(ctx); err != nil {
+		return
+	}
+
+	if err = pr.LoadBaseRepoCtx(ctx); err != nil {
+		return
+	}
+
+	comment, err = models.CreateCommentCtx(ctx, &models.CreateCommentOptions{
+		Type:  typ,
+		Doer:  doer,
+		Repo:  pr.BaseRepo,
+		Issue: pr.Issue,
+	})
+	return
+}

modules/git/repo_branch_gogit.go

@@ -144,3 +144,19 @@ func (repo *Repository) WalkReferences(arg ObjectType, skip, limit int, walkfn f
 	})
 	return i, err
 }
+
+// GetRefsBySha returns all references filtered with prefix that belong to a sha commit hash
+func (repo *Repository) GetRefsBySha(sha, prefix string) ([]string, error) {
+	var revList []string
+	iter, err := repo.gogitRepo.References()
+	if err != nil {
+		return nil, err
+	}
+	err = iter.ForEach(func(ref *plumbing.Reference) error {
+		if ref.Hash().String() == sha && strings.HasPrefix(string(ref.Name()), prefix) {
+			revList = append(revList, string(ref.Name()))
+		}
+		return nil
+	})
+	return revList, err
+}

modules/git/repo_branch_nogogit.go

@@ -190,3 +190,15 @@ func walkShowRef(ctx context.Context, repoPath, arg string, skip, limit int, wal
 	}
 	return i, nil
 }
+
+// GetRefsBySha returns all references filtered with prefix that belong to a sha commit hash
+func (repo *Repository) GetRefsBySha(sha, prefix string) ([]string, error) {
+	var revList []string
+	_, err := walkShowRef(repo.Ctx, repo.Path, "", 0, 0, func(walkSha, refname string) error {
+		if walkSha == sha && strings.HasPrefix(refname, prefix) {
+			revList = append(revList, refname)
+		}
+		return nil
+	})
+	return revList, err
+}

modules/git/repo_branch_test.go

@@ -54,3 +54,44 @@ func BenchmarkRepository_GetBranches(b *testing.B) {
 		}
 	}
 }
+
+func TestGetRefsBySha(t *testing.T) {
+	bareRepo5Path := filepath.Join(testReposDir, "repo5_pulls")
+	bareRepo5, err := OpenRepository(DefaultContext, bareRepo5Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer bareRepo5.Close()
+
+	// do not exist
+	branches, err := bareRepo5.GetRefsBySha("8006ff9adbf0cb94da7dad9e537e53817f9fa5c0", "")
+	assert.NoError(t, err)
+	assert.Len(t, branches, 0)
+
+	// refs/pull/1/head
+	branches, err = bareRepo5.GetRefsBySha("c83380d7056593c51a699d12b9c00627bd5743e9", PullPrefix)
+	assert.NoError(t, err)
+	assert.EqualValues(t, []string{"refs/pull/1/head"}, branches)
+
+	branches, err = bareRepo5.GetRefsBySha("d8e0bbb45f200e67d9a784ce55bd90821af45ebd", BranchPrefix)
+	assert.NoError(t, err)
+	assert.EqualValues(t, []string{"refs/heads/master", "refs/heads/master-clone"}, branches)
+
+	branches, err = bareRepo5.GetRefsBySha("58a4bcc53ac13e7ff76127e0fb518b5262bf09af", BranchPrefix)
+	assert.NoError(t, err)
+	assert.EqualValues(t, []string{"refs/heads/test-patch-1"}, branches)
+}
+
+func BenchmarkGetRefsBySha(b *testing.B) {
+	bareRepo5Path := filepath.Join(testReposDir, "repo5_pulls")
+	bareRepo5, err := OpenRepository(DefaultContext, bareRepo5Path)
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer bareRepo5.Close()
+
+	_, _ = bareRepo5.GetRefsBySha("8006ff9adbf0cb94da7dad9e537e53817f9fa5c0", "")
+	_, _ = bareRepo5.GetRefsBySha("d8e0bbb45f200e67d9a784ce55bd90821af45ebd", "")
+	_, _ = bareRepo5.GetRefsBySha("c83380d7056593c51a699d12b9c00627bd5743e9", "")
+	_, _ = bareRepo5.GetRefsBySha("58a4bcc53ac13e7ff76127e0fb518b5262bf09af", "")
+}

modules/git/tests/repos/repo5_pulls/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/master

modules/git/tests/repos/repo5_pulls/config

@@ -0,0 +1,6 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = true
+[receive]
+	advertisePushOptions = true

modules/git/tests/repos/repo5_pulls/description

@@ -0,0 +1 @@
+Unnamed repository; edit this file 'description' to name the repository.

modules/git/tests/repos/repo5_pulls/info/exclude

@@ -0,0 +1,6 @@
+# git ls-files --others --exclude-from=.git/info/exclude
+# Lines that start with '#' are comments.
+# For a project mostly in C, the following would be a good set of
+# exclude patterns (uncomment them if you want to use them):
+# *.[oa]
+# *~

modules/git/tests/repos/repo5_pulls/objects/58/a4bcc53ac13e7ff76127e0fb518b5262bf09af

@@ -0,0 +1 @@
+x
%<25>НnУ0<0C>;ы)И0H<30>њ1	P<>]кє
(<28>F2ИTх§kЗ7|Иwu]<5D>{Oєв<D194><19>HЈВpЎ<70>8Г$A<>1І"\ЂЊaТRfї<66>fп4л<0B>й#ZL:JЪ\-<2D>Ђ#fO2sАЂN<D082>§Ж6шігЏгчNЛ;яvМХ#њш	3p<>ЋзК5<D09A><35><EFBFBD>pкy^<5E>ЕхyдўL)xклМs_<0F>n№1]ооЇaб_<D0B1>)@X

modules/git/tests/repos/repo5_pulls/objects/bf/4dc0709be60f043821351ff4bb2b17e5cabbb2

@@ -0,0 +1,2 @@
+x
­ŹMNÄ0…Y÷Öl„ś'Ť„€ ‰ťi%úŁ4ÜźÄ
Ř<=ů}~˛ó2MccÜM«" ˘ČhÖ¬zŽ±÷)q(<28>•CRIŠO¤¸tk¬27Č˝1=˛GrL&]ŘYťBFtÚ'&oŤ„?^¸/–u‰”´ŐčŃŃľ®‚*ÄL<C384>­ŘÝ›ŇĹŻ6,¶\ǵĹO©íöô
+ď˛5řؤžî#xjűěĺ<C49B>‡CžA9<41>VyB÷¨»üóc“˙iëޤ^RŤsŕ<Ĺmo>Ă8·Ž.kly¸¨îC©ič

modules/git/tests/repos/repo5_pulls/objects/d8/e0bbb45f200e67d9a784ce55bd90821af45ebd

@@ -0,0 +1,2 @@
+x
­ŽAJAE]÷)Š¬"‚VwWĎt E˛ÄŤz€NU5Ě$ôTö9<C3B6>¸ň&Ţ$'1Ń+¸y|ţ<>Ďçífł6=^XS…NpEĚ…"ÍRĚ1v>W–(Ň®•gD©ŢíJÓÁ@%W’PKZ
+Řc—2ŠźůšD2)ťr¬®ěímŰ`ä¶ŢYy×fÓÉĽčhđ:j›\Ţü)<29>Ű©»=ăúŚř."ů>ůW˙~6ýź5w<|>>Ü/źž—ÇĂ|
˘mp?<3F>
Xó

modules/git/tests/repos/repo5_pulls/objects/ed/8f4d2fa5b2420706580d191f5dd50c4e491f3f

@@ -0,0 +1,3 @@
+x
­ŽAJAE]÷)Š¬!V×ÌtMƒˆ"YâF=@uw5Ì$ô”ûD\yo’“hô
+nÞâ?ø¼¼ÝlÖÄxbMd ,ƒTŸ<54>˜C7f%äÈuÄ”¼PŒÜ3Jr;i:ÔŽJ,µ`”€5øP)úa¬Ì”µ”1Æž
+9y³—mƒ9·õÎäU›<EFBFBD>.nàIgƒçYÛâìâOÁ¥ýl×G,<2C>¸:ì=÷q€s$D—›MÿçÍö÷w·«‡ÇÕaÿ_ŸSÑ6¹o9X‚

modules/git/tests/repos/repo5_pulls/objects/info/packs

@@ -0,0 +1,2 @@
+P pack-81423f591973f5d9dab89cc45afa1c544448133e.pack
+

modules/git/tests/repos/repo5_pulls/packed-refs

@@ -0,0 +1,5 @@
+# pack-refs with: peeled fully-peeled sorted 
+c83380d7056593c51a699d12b9c00627bd5743e9 refs/heads/test-patch-1
+c83380d7056593c51a699d12b9c00627bd5743e9 refs/pull/1/head
+111cac04bd7d20301964e27a93698aabb5781b80 refs/pull/1/merge
+72866af952e98d02a73003501836074b286a78f6 refs/tags/v0.9.99

modules/git/tests/repos/repo5_pulls/refs/heads/master

@@ -0,0 +1 @@
+d8e0bbb45f200e67d9a784ce55bd90821af45ebd

modules/git/tests/repos/repo5_pulls/refs/heads/master-clone

@@ -0,0 +1 @@
+d8e0bbb45f200e67d9a784ce55bd90821af45ebd

modules/git/tests/repos/repo5_pulls/refs/heads/test-patch-1

@@ -0,0 +1 @@
+58a4bcc53ac13e7ff76127e0fb518b5262bf09af

modules/git/tests/repos/repo5_pulls/refs/pull/4/head

@@ -0,0 +1 @@
+58a4bcc53ac13e7ff76127e0fb518b5262bf09af

options/locale/locale_en-US.ini

@@ -1560,6 +1560,14 @@ pulls.squash_merge_pull_request = Create squash commit
 pulls.merge_manually = Manually merged
 pulls.merge_commit_id = The merge commit ID
 pulls.require_signed_wont_sign = The branch requires signed commits but this merge will not be signed
+pulls.merge_pull_request_now = Merge Pull Request Now
+pulls.rebase_merge_pull_request_now = Rebase and Merge Now
+pulls.rebase_merge_commit_pull_request_now = Rebase and Merge Now (--no-ff)
+pulls.squash_merge_pull_request_now = Squash and Merge Now
+pulls.merge_pull_request_on_status_success = Merge Pull Request When All Checks Succeed
+pulls.rebase_merge_pull_request_on_status_success = Rebase and Merge When All Checks Succeed
+pulls.rebase_merge_commit_pull_request_on_status_success = Rebase and Merge (--no-ff) When All Checks Succeed
+pulls.squash_merge_pull_request_on_status_success = Squash and Merge When All Checks Succeed
 pulls.invalid_merge_option = You cannot use this merge option for this pull request.
 pulls.merge_conflict = Merge Failed: There was a conflict whilst merging. Hint: Try a different strategy
 pulls.merge_conflict_summary = Error Message
@@ -1588,9 +1596,16 @@ pulls.outdated_with_base_branch = This branch is out-of-date with the base branc
 pulls.closed_at = `closed this pull request <a id="%[1]s" href="#%[1]s">%[2]s</a>`
 pulls.reopened_at = `reopened this pull request <a id="%[1]s" href="#%[1]s">%[2]s</a>`
 pulls.merge_instruction_hint = `You can also view <a class="show-instruction">command line instructions</a>.`
-
 pulls.merge_instruction_step1_desc = From your project repository, check out a new branch and test the changes.
 pulls.merge_instruction_step2_desc = Merge the changes and update on Gitea.
+pulls.merge_on_status_success = The pull request was scheduled to merge when all checks succeed.
+pulls.merge_on_status_success_already_scheduled = This pull request is already scheduled to merge when all checks succeed.
+pulls.pr_has_pending_merge_on_success = %[1]s scheduled this pull request to auto merge when all checks succeed %[2]s.
+pulls.merge_pull_on_success_cancel = Cancel auto merge
+pulls.pull_request_not_scheduled = This pull request is not scheduled to auto merge.
+pulls.pull_request_schedule_canceled = The auto merge was canceled for this pull request.
+pulls.pull_request_scheduled_auto_merge = `scheduled this pull request to auto merge when all checks succeed %[1]s`
+pulls.pull_request_canceled_scheduled_auto_merge = `canceled auto merging this pull request when all checks succeed %[1]s`
 
 milestones.new = New Milestone
 milestones.open_tab = %d Open

routers/api/v1/api.go

@@ -984,7 +984,8 @@ func Routes() *web.Route {
 						m.Post("/update", reqToken(), repo.UpdatePullRequest)
 						m.Get("/commits", repo.GetPullRequestCommits)
 						m.Combo("/merge").Get(repo.IsPullRequestMerged).
-							Post(reqToken(), mustNotBeArchived, bind(forms.MergePullRequestForm{}), repo.MergePullRequest)
+							Post(reqToken(), mustNotBeArchived, bind(forms.MergePullRequestForm{}), repo.MergePullRequest).
+							Delete(reqToken(), mustNotBeArchived, repo.CancelScheduledAutoMerge)
 						m.Group("/reviews", func() {
 							m.Combo("").
 								Get(repo.ListPullReviews).

routers/api/v1/repo/pull.go

@@ -15,6 +15,7 @@ import (
 
 	"code.gitea.io/gitea/models"
 	issues_model "code.gitea.io/gitea/models/issues"
+	pull_model "code.gitea.io/gitea/models/pull"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
@@ -28,6 +29,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/routers/api/v1/utils"
 	asymkey_service "code.gitea.io/gitea/services/asymkey"
+	"code.gitea.io/gitea/services/automerge"
 	"code.gitea.io/gitea/services/forms"
 	issue_service "code.gitea.io/gitea/services/issue"
 	pull_service "code.gitea.io/gitea/services/pull"
@@ -805,6 +807,22 @@ func MergePullRequest(ctx *context.APIContext) {
 		return
 	}
 
+	if form.MergeWhenChecksSucceed {
+		scheduled, err := automerge.ScheduleAutoMerge(ctx, ctx.Doer, pr, repo_model.MergeStyle(form.Do), form.MergeTitleField)
+		if err != nil {
+			if pull_model.IsErrAlreadyScheduledToAutoMerge(err) {
+				ctx.Error(http.StatusConflict, "ScheduleAutoMerge", err)
+				return
+			}
+			ctx.Error(http.StatusInternalServerError, "ScheduleAutoMerge", err)
+			return
+		} else if scheduled {
+			// nothing more to do ...
+			ctx.Status(http.StatusCreated)
+			return
+		}
+	}
+
 	if err := pull_service.Merge(pr, ctx.Doer, ctx.Repo.GitRepo, repo_model.MergeStyle(form.Do), form.HeadCommitID, form.MergeTitleField); err != nil {
 		if models.IsErrInvalidMergeStyle(err) {
 			ctx.Error(http.StatusMethodNotAllowed, "Invalid merge style", fmt.Errorf("%s is not allowed an allowed merge style for this repository", repo_model.MergeStyle(form.Do)))
@@ -1113,6 +1131,78 @@ func UpdatePullRequest(ctx *context.APIContext) {
 	ctx.Status(http.StatusOK)
 }
 
+// MergePullRequest cancel an auto merge scheduled for a given PullRequest by index
+func CancelScheduledAutoMerge(ctx *context.APIContext) {
+	// swagger:operation DELETE /repos/{owner}/{repo}/pulls/{index}/merge repository repoCancelScheduledAutoMerge
+	// ---
+	// summary: Cancel the scheduled auto merge for the given pull request
+	// produces:
+	// - application/json
+	// parameters:
+	// - name: owner
+	//   in: path
+	//   description: owner of the repo
+	//   type: string
+	//   required: true
+	// - name: repo
+	//   in: path
+	//   description: name of the repo
+	//   type: string
+	//   required: true
+	// - name: index
+	//   in: path
+	//   description: index of the pull request to merge
+	//   type: integer
+	//   format: int64
+	//   required: true
+	// responses:
+	//   "204":
+	//     "$ref": "#/responses/empty"
+	//   "403":
+	//     "$ref": "#/responses/forbidden"
+	//   "404":
+	//     "$ref": "#/responses/notFound"
+
+	pullIndex := ctx.ParamsInt64(":index")
+	pull, err := models.GetPullRequestByIndex(ctx.Repo.Repository.ID, pullIndex)
+	if err != nil {
+		if models.IsErrPullRequestNotExist(err) {
+			ctx.NotFound()
+			return
+		}
+		ctx.InternalServerError(err)
+		return
+	}
+
+	exist, autoMerge, err := pull_model.GetScheduledMergeByPullID(ctx, pull.ID)
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+	if !exist {
+		ctx.NotFound()
+		return
+	}
+
+	if ctx.Doer.ID != autoMerge.DoerID {
+		allowed, err := models.IsUserRepoAdminCtx(ctx, ctx.Repo.Repository, ctx.Doer)
+		if err != nil {
+			ctx.InternalServerError(err)
+			return
+		}
+		if !allowed {
+			ctx.Error(http.StatusForbidden, "No permission to cancel", "user has no permission to cancel the scheduled auto merge")
+			return
+		}
+	}
+
+	if err := pull_model.RemoveScheduledAutoMerge(ctx, ctx.Doer, pull.ID, true); err != nil {
+		ctx.InternalServerError(err)
+	} else {
+		ctx.Status(http.StatusNoContent)
+	}
+}
+
 // GetPullRequestCommits gets all commits associated with a given PR
 func GetPullRequestCommits(ctx *context.APIContext) {
 	// swagger:operation GET /repos/{owner}/{repo}/pulls/{index}/commits repository repoGetPullRequestCommits

routers/init.go

@@ -39,6 +39,7 @@ import (
 	web_routers "code.gitea.io/gitea/routers/web"
 	"code.gitea.io/gitea/services/auth"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
+	"code.gitea.io/gitea/services/automerge"
 	"code.gitea.io/gitea/services/cron"
 	"code.gitea.io/gitea/services/mailer"
 	repo_migrations "code.gitea.io/gitea/services/migrations"
@@ -147,6 +148,7 @@ func GlobalInitInstalled(ctx context.Context) {
 	mirror_service.InitSyncMirrors()
 	mustInit(webhook.Init)
 	mustInit(pull_service.Init)
+	mustInit(automerge.Init)
 	mustInit(task.Init)
 	mustInit(repo_migrations.Init)
 	eventsource.GetManager().Init()

routers/web/repo/issue.go

@@ -24,6 +24,7 @@ import (
 	issues_model "code.gitea.io/gitea/models/issues"
 	"code.gitea.io/gitea/models/organization"
 	project_model "code.gitea.io/gitea/models/project"
+	pull_model "code.gitea.io/gitea/models/pull"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
@@ -1662,6 +1663,13 @@ func ViewIssue(ctx *context.Context) {
 		}
 
 		ctx.Data["StillCanManualMerge"] = stillCanManualMerge()
+
+		// Check if there is a pending pr merge
+		ctx.Data["HasPendingPullRequestMerge"], ctx.Data["PendingPullRequestMerge"], err = pull_model.GetScheduledMergeByPullID(ctx, pull.ID)
+		if err != nil {
+			ctx.ServerError("GetScheduledMergeByPullID", err)
+			return
+		}
 	}
 
 	// Get Dependencies

services/automerge/automerge.go

@@ -0,0 +1,241 @@
+// Copyright 2021 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 automerge
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"code.gitea.io/gitea/models"
+	pull_model "code.gitea.io/gitea/models/pull"
+	repo_model "code.gitea.io/gitea/models/repo"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/process"
+	"code.gitea.io/gitea/modules/queue"
+	pull_service "code.gitea.io/gitea/services/pull"
+)
+
+// prAutoMergeQueue represents a queue to handle update pull request tests
+var prAutoMergeQueue queue.UniqueQueue
+
+// Init runs the task queue to that handles auto merges
+func Init() error {
+	prAutoMergeQueue = queue.CreateUniqueQueue("pr_auto_merge", handle, "")
+	if prAutoMergeQueue == nil {
+		return fmt.Errorf("Unable to create pr_auto_merge Queue")
+	}
+	go graceful.GetManager().RunWithShutdownFns(prAutoMergeQueue.Run)
+	return nil
+}
+
+// handle passed PR IDs and test the PRs
+func handle(data ...queue.Data) []queue.Data {
+	for _, d := range data {
+		var id int64
+		var sha string
+		if _, err := fmt.Sscanf(d.(string), "%d_%s", &id, &sha); err != nil {
+			log.Error("could not parse data from pr_auto_merge queue (%v): %v", d, err)
+			continue
+		}
+		handlePull(id, sha)
+	}
+	return nil
+}
+
+func addToQueue(pr *models.PullRequest, sha string) {
+	if err := prAutoMergeQueue.PushFunc(fmt.Sprintf("%d_%s", pr.ID, sha), func() error {
+		log.Trace("Adding pullID: %d to the pull requests patch checking queue with sha %s", pr.ID, sha)
+		return nil
+	}); err != nil {
+		log.Error("Error adding pullID: %d to the pull requests patch checking queue %v", pr.ID, err)
+	}
+}
+
+// ScheduleAutoMerge if schedule is false and no error, pull can be merged directly
+func ScheduleAutoMerge(ctx context.Context, doer *user_model.User, pull *models.PullRequest, style repo_model.MergeStyle, message string) (scheduled bool, err error) {
+	lastCommitStatus, err := pull_service.GetPullRequestCommitStatusState(ctx, pull)
+	if err != nil {
+		return false, err
+	}
+
+	// we don't need to schedule
+	if lastCommitStatus.IsSuccess() {
+		return false, nil
+	}
+
+	return true, pull_model.ScheduleAutoMerge(ctx, doer, pull.ID, style, message)
+}
+
+// MergeScheduledPullRequest merges a previously scheduled pull request when all checks succeeded
+func MergeScheduledPullRequest(ctx context.Context, sha string, repo *repo_model.Repository) error {
+	pulls, err := getPullRequestsByHeadSHA(ctx, sha, repo, func(pr *models.PullRequest) bool {
+		return !pr.HasMerged && pr.CanAutoMerge()
+	})
+	if err != nil {
+		return err
+	}
+
+	for _, pr := range pulls {
+		addToQueue(pr, sha)
+	}
+
+	return nil
+}
+
+func getPullRequestsByHeadSHA(ctx context.Context, sha string, repo *repo_model.Repository, filter func(*models.PullRequest) bool) (map[int64]*models.PullRequest, error) {
+	gitRepo, err := git.OpenRepository(ctx, repo.RepoPath())
+	if err != nil {
+		return nil, err
+	}
+	defer gitRepo.Close()
+
+	refs, err := gitRepo.GetRefsBySha(sha, "")
+	if err != nil {
+		return nil, err
+	}
+
+	pulls := make(map[int64]*models.PullRequest)
+
+	for _, ref := range refs {
+		// Each pull branch starts with refs/pull/ we then go from there to find the index of the pr and then
+		// use that to get the pr.
+		if strings.HasPrefix(ref, git.PullPrefix) {
+			parts := strings.Split(ref[len(git.PullPrefix):], "/")
+
+			// e.g. 'refs/pull/1/head' would be []string{"1", "head"}
+			if len(parts) != 2 {
+				log.Error("getPullRequestsByHeadSHA found broken pull ref [%s] on repo [%-v]", ref, repo)
+				continue
+			}
+
+			prIndex, err := strconv.ParseInt(parts[0], 10, 64)
+			if err != nil {
+				log.Error("getPullRequestsByHeadSHA found broken pull ref [%s] on repo [%-v]", ref, repo)
+				continue
+			}
+
+			p, err := models.GetPullRequestByIndexCtx(ctx, repo.ID, prIndex)
+			if err != nil {
+				// If there is no pull request for this branch, we don't try to merge it.
+				if models.IsErrPullRequestNotExist(err) {
+					continue
+				}
+				return nil, err
+			}
+
+			if filter(p) {
+				pulls[p.ID] = p
+			}
+		}
+	}
+
+	return pulls, nil
+}
+
+func handlePull(pullID int64, sha string) {
+	ctx, _, finished := process.GetManager().AddContext(graceful.GetManager().HammerContext(),
+		fmt.Sprintf("Handle AutoMerge of pull[%d] with sha[%s]", pullID, sha))
+	defer finished()
+
+	pr, err := models.GetPullRequestByID(ctx, pullID)
+	if err != nil {
+		log.Error("GetPullRequestByID[%d]: %v", pullID, err)
+		return
+	}
+
+	// Check if there is a scheduled pr in the db
+	exists, scheduledPRM, err := pull_model.GetScheduledMergeByPullID(ctx, pr.ID)
+	if err != nil {
+		log.Error("pull[%d] GetScheduledMergeByPullID: %v", pr.ID, err)
+		return
+	}
+	if !exists {
+		return
+	}
+
+	// Get all checks for this pr
+	// We get the latest sha commit hash again to handle the case where the check of a previous push
+	// did not succeed or was not finished yet.
+
+	if err = pr.LoadHeadRepoCtx(ctx); err != nil {
+		log.Error("pull[%d] LoadHeadRepoCtx: %v", pr.ID, err)
+		return
+	}
+
+	headGitRepo, err := git.OpenRepository(ctx, pr.HeadRepo.RepoPath())
+	if err != nil {
+		log.Error("OpenRepository: %v", err)
+		return
+	}
+	defer headGitRepo.Close()
+
+	headBranchExist := headGitRepo.IsBranchExist(pr.HeadBranch)
+
+	if pr.HeadRepo == nil || !headBranchExist {
+		log.Warn("Head branch of auto merge pr does not exist [HeadRepoID: %d, Branch: %s, PR ID: %d]", pr.HeadRepoID, pr.HeadBranch, pr.ID)
+		return
+	}
+
+	// Check if all checks succeeded
+	pass, err := pull_service.IsPullCommitStatusPass(ctx, pr)
+	if err != nil {
+		log.Error("IsPullCommitStatusPass: %v", err)
+		return
+	}
+	if !pass {
+		log.Info("Scheduled auto merge pr has unsuccessful status checks [PullID: %d]", pr.ID)
+		return
+	}
+
+	// Merge if all checks succeeded
+	doer, err := user_model.GetUserByIDCtx(ctx, scheduledPRM.DoerID)
+	if err != nil {
+		log.Error("GetUserByIDCtx: %v", err)
+		return
+	}
+
+	perm, err := models.GetUserRepoPermission(ctx, pr.HeadRepo, doer)
+	if err != nil {
+		log.Error("GetUserRepoPermission: %v", err)
+		return
+	}
+
+	if err := pull_service.CheckPullMergable(ctx, doer, &perm, pr, false, false); err != nil {
+		if errors.Is(pull_service.ErrUserNotAllowedToMerge, err) {
+			log.Info("PR %d was scheduled to automerge by an unauthorized user", pr.ID)
+			return
+		}
+		log.Error("pull[%d] CheckPullMergable: %v", pr.ID, err)
+		return
+	}
+
+	var baseGitRepo *git.Repository
+	if pr.BaseRepoID == pr.HeadRepoID {
+		baseGitRepo = headGitRepo
+	} else {
+		if err = pr.LoadBaseRepoCtx(ctx); err != nil {
+			log.Error("LoadBaseRepoCtx: %v", err)
+			return
+		}
+
+		baseGitRepo, err = git.OpenRepository(ctx, pr.BaseRepo.RepoPath())
+		if err != nil {
+			log.Error("OpenRepository: %v", err)
+			return
+		}
+		defer baseGitRepo.Close()
+	}
+
+	if err := pull_service.Merge(pr, doer, baseGitRepo, scheduledPRM.MergeStyle, "", scheduledPRM.Message); err != nil {
+		log.Error("pull_service.Merge: %v", err)
+		return
+	}
+}

services/forms/repo_form.go

@@ -592,6 +592,7 @@ type MergePullRequestForm struct {
 	MergeCommitID          string // only used for manually-merged
 	HeadCommitID           string `json:"head_commit_id,omitempty"`
 	ForceMerge             *bool  `json:"force_merge,omitempty"`
+	MergeWhenChecksSucceed bool   `json:"merge_when_checks_succeed,omitempty"`
 	DeleteBranchAfterMerge bool   `json:"delete_branch_after_merge,omitempty"`
 }
 

services/pull/commit_status.go

@@ -137,5 +137,13 @@ func GetPullRequestCommitStatusState(ctx context.Context, pr *models.PullRequest
 		return "", errors.Wrap(err, "GetLatestCommitStatus")
 	}
 
-	return MergeRequiredContextsCommitStatus(commitStatuses, pr.ProtectedBranch.StatusCheckContexts), nil
+	if err := pr.LoadProtectedBranchCtx(ctx); err != nil {
+		return "", errors.Wrap(err, "LoadProtectedBranch")
+	}
+	var requiredContexts []string
+	if pr.ProtectedBranch != nil {
+		requiredContexts = pr.ProtectedBranch.StatusCheckContexts
+	}
+
+	return MergeRequiredContextsCommitStatus(commitStatuses, requiredContexts), nil
 }

services/pull/merge.go

@@ -18,6 +18,7 @@ import (
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/models/db"
+	pull_model "code.gitea.io/gitea/models/pull"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
@@ -46,6 +47,11 @@ func Merge(pr *models.PullRequest, doer *user_model.User, baseGitRepo *git.Repos
 	pullWorkingPool.CheckIn(fmt.Sprint(pr.ID))
 	defer pullWorkingPool.CheckOut(fmt.Sprint(pr.ID))
 
+	// Removing an auto merge pull and ignore if not exist
+	if err := pull_model.RemoveScheduledAutoMerge(db.DefaultContext, doer, pr.ID, false); err != nil && !models.IsErrNotExist(err) {
+		return err
+	}
+
 	prUnit, err := pr.BaseRepo.GetUnit(unit.TypePullRequests)
 	if err != nil {
 		log.Error("pr.BaseRepo.GetUnit(unit.TypePullRequests): %v", err)

services/pull/pull.go

@@ -253,7 +253,7 @@ func AddTestPullRequestTask(doer *user_model.User, repoID int64, branch string,
 	graceful.GetManager().RunWithShutdownContext(func(ctx context.Context) {
 		// There is no sensible way to shut this down ":-("
 		// If you don't let it run all the way then you will lose data
-		// FIXME: graceful: AddTestPullRequestTask needs to become a queue!
+		// TODO: graceful: AddTestPullRequestTask needs to become a queue!
 
 		prs, err := models.GetUnmergedPullRequestsByHeadInfo(repoID, branch)
 		if err != nil {

services/repository/files/commit.go

@@ -14,6 +14,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/services/automerge"
 )
 
 // CreateCommitStatus creates a new CommitStatus given a bunch of parameters
@@ -44,6 +45,12 @@ func CreateCommitStatus(ctx context.Context, repo *repo_model.Repository, creato
 		return fmt.Errorf("NewCommitStatus[repo_id: %d, user_id: %d, sha: %s]: %v", repo.ID, creator.ID, sha, err)
 	}
 
+	if status.State.IsSuccess() {
+		if err := automerge.MergeScheduledPullRequest(ctx, sha, repo); err != nil {
+			return fmt.Errorf("MergeScheduledPullRequest[repo_id: %d, user_id: %d, sha: %s]: %w", repo.ID, creator.ID, sha, err)
+		}
+	}
+
 	return nil
 }
 

templates/repo/issue/view_content/comments.tmpl

@@ -10,7 +10,8 @@
 		22 = REVIEW, 23 = ISSUE_LOCKED, 24 = ISSUE_UNLOCKED, 25 = TARGET_BRANCH_CHANGED,
 		26 = DELETE_TIME_MANUAL, 27 = REVIEW_REQUEST, 28 = MERGE_PULL_REQUEST,
 		29 = PULL_PUSH_EVENT, 30 = PROJECT_CHANGED, 31 = PROJECT_BOARD_CHANGED
-		32 = DISMISSED_REVIEW -->
+		32 = DISMISSED_REVIEW, 33 = COMMENT_TYPE_CHANGE_ISSUE_REF, 34 = PR_SCHEDULE_TO_AUTO_MERGE,
+		35 = CANCEL_SCHEDULED_AUTO_MERGE_PR -->
 		{{if eq .Type 0}}
 			<div class="timeline-item comment" id="{{.HashTag}}">
 			{{if .OriginalAuthor }}
@@ -837,6 +838,15 @@
 					{{end}}
 				</span>
 			</div>
+		{{else if or (eq .Type 34) (eq .Type 35)}}
+			<div class="timeline-item event" id="{{.HashTag}}">
+				<span class="badge">{{svg "octicon-git-merge" 16}}</span>
+				<span class="text grey">
+					<a class="author" href="{{.Poster.HomeLink}}">{{.Poster.GetDisplayName}}</a>
+					{{if eq .Type 34}}{{$.i18n.Tr "repo.pulls.pull_request_scheduled_auto_merge" $createdStr | Safe}}
+					{{else}}{{$.i18n.Tr "repo.pulls.pull_request_canceled_scheduled_auto_merge" $createdStr | Safe}}{{end}}
+				</span>
+			</div>
 		{{end}}
 	{{end}}
 {{end}}

templates/swagger/v1_json.tmpl

@@ -8015,6 +8015,51 @@
             "$ref": "#/responses/error"
           }
         }
+      },
+      "delete": {
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "repository"
+        ],
+        "summary": "Cancel the scheduled auto merge for the given pull request",
+        "operationId": "repoCancelScheduledAutoMerge",
+        "parameters": [
+          {
+            "type": "string",
+            "description": "owner of the repo",
+            "name": "owner",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "name of the repo",
+            "name": "repo",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "integer",
+            "format": "int64",
+            "description": "index of the pull request to merge",
+            "name": "index",
+            "in": "path",
+            "required": true
+          }
+        ],
+        "responses": {
+          "204": {
+            "$ref": "#/responses/empty"
+          },
+          "403": {
+            "$ref": "#/responses/forbidden"
+          },
+          "404": {
+            "$ref": "#/responses/notFound"
+          }
+        }
       }
     },
     "/repos/{owner}/{repo}/pulls/{index}/requested_reviewers": {
@@ -16298,6 +16343,10 @@
         "head_commit_id": {
           "type": "string",
           "x-go-name": "HeadCommitID"
+        },
+        "merge_when_checks_succeed": {
+          "type": "boolean",
+          "x-go-name": "MergeWhenChecksSucceed"
         }
       },
       "x-go-name": "MergePullRequestForm",