perf(pull): load the repository once for all commit statuses (#39930) (#40135)

Backport #39930 by @lunny

Pages showing commit statuses loaded the repository of every status
separately, so a PR with ~75 statuses ran ~75 identical repository
queries per merge box render (about 3.4s in a production trace).
`statusRepoCanReadActions` only loaded the repository inside the
permission cache loader, which never runs once `RepoAssignment` has
published the permission.

- `CommitStatus.loadRepository` resolves through the request context
cache
- `statusRepoCanReadActions` loads the repository before the permission
lookup
- `RepoAssignment` publishes its repository to the context cache next to
the permission
- `GetCommitActionsStatusMap` drops its own repository map

Queries per request with 50 statuses (45 Actions, 5 external) on the
head commit, SQLite:

| Page | Repository queries | Total queries |
|---|---|---|
| PR view | 61 → 11 | 157 → 107 |
| Commit | 6 → 5 | 24 → 23 |
| Branches | 6 → 5 | 33 → 32 |
| Commits | 6 → 5 | 23 → 22 |
| Repo home | 8 → 7 | 35 → 34 |
| `/pulls` | 15 → 15 | 37 → 37 |

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

models/git/commit_status.go

@@ -182,7 +182,7 @@ func GetNextCommitStatusIndex(ctx context.Context, repoID int64, sha string) (in
 
 func (status *CommitStatus) loadRepository(ctx context.Context) (err error) {
 	if status.Repo == nil {
-		status.Repo, err = repo_model.GetRepositoryByID(ctx, status.RepoID)
+		status.Repo, err = cache.GetWithContextCache(ctx, cachegroup.Repository, status.RepoID, repo_model.GetRepositoryByID)
 		if err != nil {
 			return fmt.Errorf("getRepositoryByID [%d]: %w", status.RepoID, err)
 		}
@@ -230,11 +230,9 @@ func (status *CommitStatus) cutTargetURLGiteaActionsPrefix(ctx context.Context)
 		return "", false
 	}
 
-	if status.Repo == nil {
-		if err := status.loadRepository(ctx); err != nil {
-			log.Error("loadRepository: %v", err)
-			return "", false
-		}
+	if err := status.loadRepository(ctx); err != nil {
+		log.Error("loadRepository: %v", err)
+		return "", false
 	}
 
 	prefix := status.Repo.Link() + "/actions"
@@ -572,11 +570,12 @@ func SignCommitsApplyDoerPermission(ctx context.Context, doer *user_model.User,
 }
 
 func statusRepoCanReadActions(ctx context.Context, doer *user_model.User, status *CommitStatus) bool {
+	if err := status.loadRepository(ctx); err != nil {
+		log.Error("loadRepository: %v", err)
+		return false
+	}
 	perm, err := cache.GetWithContextCache(ctx, cachegroup.RepoUserPermission, access_model.RepoUserPermissionCacheKey(status.RepoID, doer),
-		func(ctx context.Context, _ string) (access_model.Permission, error) { // only runs on a cache miss
-			if err := status.loadRepository(ctx); err != nil {
-				return access_model.Permission{}, err
-			}
+		func(ctx context.Context, _key string) (access_model.Permission, error) {
 			return access_model.GetDoerRepoPermission(ctx, status.Repo, doer)
 		},
 	)