Do DB update after merge in hammer context (#21401) (#21416)

Backport #21401

When merge was changed to run in the background context, the db updates
were still running in request context. This means that the merge could
be successful but the db not be updated.

This PR changes both these to run in the hammer context, this is not
complete rollback protection but it's much better.

Fix #21332

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/pull/merge.go

@@ -28,6 +28,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/graceful"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/notification"
 	"code.gitea.io/gitea/modules/references"
@@ -165,9 +166,10 @@ func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.U
 		go AddTestPullRequestTask(doer, pr.BaseRepo.ID, pr.BaseBranch, false, "", "")
 	}()
 
-	// TODO: make it able to do this in a database session
-	mergeCtx := context.Background()
-	pr.MergedCommitID, err = rawMerge(mergeCtx, pr, doer, mergeStyle, expectedHeadCommitID, message)
+	// Run the merge in the hammer context to prevent cancellation
+	hammerCtx := graceful.GetManager().HammerContext()
+
+	pr.MergedCommitID, err = rawMerge(hammerCtx, pr, doer, mergeStyle, expectedHeadCommitID, message)
 	if err != nil {
 		return err
 	}
@@ -176,18 +178,18 @@ func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.U
 	pr.Merger = doer
 	pr.MergerID = doer.ID
 
-	if _, err := pr.SetMerged(ctx); err != nil {
+	if _, err := pr.SetMerged(hammerCtx); err != nil {
 		log.Error("setMerged [%d]: %v", pr.ID, err)
 	}
 
-	if err := pr.LoadIssueCtx(ctx); err != nil {
+	if err := pr.LoadIssueCtx(hammerCtx); err != nil {
 		log.Error("loadIssue [%d]: %v", pr.ID, err)
 	}
 
-	if err := pr.Issue.LoadRepo(ctx); err != nil {
+	if err := pr.Issue.LoadRepo(hammerCtx); err != nil {
 		log.Error("loadRepo for issue [%d]: %v", pr.ID, err)
 	}
-	if err := pr.Issue.Repo.GetOwner(ctx); err != nil {
+	if err := pr.Issue.Repo.GetOwner(hammerCtx); err != nil {
 		log.Error("GetOwner for issue repo [%d]: %v", pr.ID, err)
 	}
 
@@ -197,17 +199,17 @@ func Merge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.U
 	cache.Remove(pr.Issue.Repo.GetCommitsCountCacheKey(pr.BaseBranch, true))
 
 	// Resolve cross references
-	refs, err := pr.ResolveCrossReferences(ctx)
+	refs, err := pr.ResolveCrossReferences(hammerCtx)
 	if err != nil {
 		log.Error("ResolveCrossReferences: %v", err)
 		return nil
 	}
 
 	for _, ref := range refs {
-		if err = ref.LoadIssueCtx(ctx); err != nil {
+		if err = ref.LoadIssueCtx(hammerCtx); err != nil {
 			return err
 		}
-		if err = ref.Issue.LoadRepo(ctx); err != nil {
+		if err = ref.Issue.LoadRepo(hammerCtx); err != nil {
 			return err
 		}
 		close := ref.RefAction == references.XRefActionCloses