feat: notify doers of a merge when automerging (#21553)

I found myself wondering whether a PR I scheduled for automerge was
actually merged. It was, but I didn't receive a mail notification for it
- that makes sense considering I am the doer and usually don't want to
receive such notifications. But ideally I want to receive a notification
when a PR was merged because I scheduled it for automerge.

This PR implements exactly that.

The implementation works, but I wonder if there's a way to avoid passing
the "This PR was automerged" state down so much. I tried solving this
via the database (checking if there's an automerge scheduled for this PR
when sending the notification) but that did not work reliably, probably
because sending the notification happens async and the entry might have
already been deleted. My implementation might be the most
straightforward but maybe not the most elegant.

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/automerge/automerge.go

@@ -257,7 +257,7 @@ func handlePull(pullID int64, sha string) {
 		defer baseGitRepo.Close()
 	}
 
-	if err := pull_service.Merge(ctx, pr, doer, baseGitRepo, scheduledPRM.MergeStyle, "", scheduledPRM.Message); err != nil {
+	if err := pull_service.Merge(ctx, pr, doer, baseGitRepo, scheduledPRM.MergeStyle, "", scheduledPRM.Message, true); err != nil {
 		log.Error("pull_service.Merge: %v", err)
 		return
 	}

services/mailer/mail.go

@@ -340,7 +340,7 @@ func createReference(issue *issues_model.Issue, comment *issues_model.Comment, a
 			extra = fmt.Sprintf("/close/%d", time.Now().UnixNano()/1e6)
 		case activities_model.ActionReopenIssue, activities_model.ActionReopenPullRequest:
 			extra = fmt.Sprintf("/reopen/%d", time.Now().UnixNano()/1e6)
-		case activities_model.ActionMergePullRequest:
+		case activities_model.ActionMergePullRequest, activities_model.ActionAutoMergePullRequest:
 			extra = fmt.Sprintf("/merge/%d", time.Now().UnixNano()/1e6)
 		case activities_model.ActionPullRequestReadyForReview:
 			extra = fmt.Sprintf("/ready/%d", time.Now().UnixNano()/1e6)
@@ -451,7 +451,7 @@ func actionToTemplate(issue *issues_model.Issue, actionType activities_model.Act
 		name = "close"
 	case activities_model.ActionReopenIssue, activities_model.ActionReopenPullRequest:
 		name = "reopen"
-	case activities_model.ActionMergePullRequest:
+	case activities_model.ActionMergePullRequest, activities_model.ActionAutoMergePullRequest:
 		name = "merge"
 	case activities_model.ActionPullReviewDismissed:
 		name = "review_dismissed"

services/mailer/mail_issue.go

@@ -25,11 +25,12 @@ func fallbackMailSubject(issue *issues_model.Issue) string {
 
 type mailCommentContext struct {
 	context.Context
-	Issue      *issues_model.Issue
-	Doer       *user_model.User
-	ActionType activities_model.ActionType
-	Content    string
-	Comment    *issues_model.Comment
+	Issue                 *issues_model.Issue
+	Doer                  *user_model.User
+	ActionType            activities_model.ActionType
+	Content               string
+	Comment               *issues_model.Comment
+	ForceDoerNotification bool
 }
 
 const (
@@ -93,7 +94,7 @@ func mailIssueCommentToParticipants(ctx *mailCommentContext, mentions []*user_mo
 	visited := make(container.Set[int64], len(unfiltered)+len(mentions)+1)
 
 	// Avoid mailing the doer
-	if ctx.Doer.EmailNotificationsPreference != user_model.EmailNotificationsAndYourOwn {
+	if ctx.Doer.EmailNotificationsPreference != user_model.EmailNotificationsAndYourOwn && !ctx.ForceDoerNotification {
 		visited.Add(ctx.Doer.ID)
 	}
 
@@ -181,17 +182,19 @@ func MailParticipants(issue *issues_model.Issue, doer *user_model.User, opType a
 	content := issue.Content
 	if opType == activities_model.ActionCloseIssue || opType == activities_model.ActionClosePullRequest ||
 		opType == activities_model.ActionReopenIssue || opType == activities_model.ActionReopenPullRequest ||
-		opType == activities_model.ActionMergePullRequest {
+		opType == activities_model.ActionMergePullRequest || opType == activities_model.ActionAutoMergePullRequest {
 		content = ""
 	}
+	forceDoerNotification := opType == activities_model.ActionAutoMergePullRequest
 	if err := mailIssueCommentToParticipants(
 		&mailCommentContext{
-			Context:    context.TODO(), // TODO: use a correct context
-			Issue:      issue,
-			Doer:       doer,
-			ActionType: opType,
-			Content:    content,
-			Comment:    nil,
+			Context:               context.TODO(), // TODO: use a correct context
+			Issue:                 issue,
+			Doer:                  doer,
+			ActionType:            opType,
+			Content:               content,
+			Comment:               nil,
+			ForceDoerNotification: forceDoerNotification,
 		}, mentions); err != nil {
 		log.Error("mailIssueCommentToParticipants: %v", err)
 	}

services/pull/merge.go

@@ -133,7 +133,7 @@ func GetDefaultMergeMessage(baseGitRepo *git.Repository, pr *issues_model.PullRe
 
 // Merge merges pull request to base repository.
 // Caller should check PR is ready to be merged (review and status checks)
-func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.User, baseGitRepo *git.Repository, mergeStyle repo_model.MergeStyle, expectedHeadCommitID, message string) error {
+func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.User, baseGitRepo *git.Repository, mergeStyle repo_model.MergeStyle, expectedHeadCommitID, message string, wasAutoMerged bool) error {
 	if err := pr.LoadHeadRepo(); err != nil {
 		log.Error("LoadHeadRepo: %v", err)
 		return fmt.Errorf("LoadHeadRepo: %w", err)
@@ -193,7 +193,11 @@ func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.U
 		log.Error("GetOwner for issue repo [%d]: %v", pr.ID, err)
 	}
 
-	notification.NotifyMergePullRequest(pr, doer)
+	if wasAutoMerged {
+		notification.NotifyAutoMergePullRequest(pr, doer)
+	} else {
+		notification.NotifyMergePullRequest(pr, doer)
+	}
 
 	// Reset cached commit count
 	cache.Remove(pr.Issue.Repo.GetCommitsCountCacheKey(pr.BaseBranch, true))