Fix duplicate status check contexts (#30660)

Caused by #30076. 

There may be some duplicate status check contexts when setting status
checks for a branch protection rule. The duplicate contexts should be
removed.

Before:
<img
src="https://github.com/go-gitea/gitea/assets/15528715/97f4de2d-4868-47a3-8a99-5a180f9ac0a3"
width="600px" />

After:
<img
src="https://github.com/go-gitea/gitea/assets/15528715/ff7289c5-9793-4090-ba31-e8cb3c85f8a3"
width="600px" />

models/git/commit_status.go

@@ -397,36 +397,16 @@ func GetLatestCommitStatusForRepoCommitIDs(ctx context.Context, repoID int64, co
 
 // FindRepoRecentCommitStatusContexts returns repository's recent commit status contexts
 func FindRepoRecentCommitStatusContexts(ctx context.Context, repoID int64, before time.Duration) ([]string, error) {
-	type result struct {
-		Index int64
-		SHA   string
-	}
-	getBase := func() *xorm.Session {
-		return db.GetEngine(ctx).Table(&CommitStatus{}).Where("repo_id = ?", repoID)
-	}
-
 	start := timeutil.TimeStampNow().AddDuration(-before)
-	results := make([]result, 0, 10)
 
-	sess := getBase().And("updated_unix >= ?", start).
-		Select("max( `index` ) as `index`, sha").
-		GroupBy("context_hash, sha").OrderBy("max( `index` ) desc")
-
-	err := sess.Find(&results)
-	if err != nil {
+	var contexts []string
+	if err := db.GetEngine(ctx).Table("commit_status").
+		Where("repo_id = ?", repoID).And("updated_unix >= ?", start).
+		Cols("context").Distinct().Find(&contexts); err != nil {
 		return nil, err
 	}
 
-	contexts := make([]string, 0, len(results))
-	if len(results) == 0 {
-		return contexts, nil
-	}
-
-	conds := make([]builder.Cond, 0, len(results))
-	for _, result := range results {
-		conds = append(conds, builder.Eq{"`index`": result.Index, "sha": result.SHA})
-	}
-	return contexts, getBase().And(builder.Or(conds...)).Select("context").Find(&contexts)
+	return contexts, nil
 }
 
 // NewCommitStatusOptions holds options for creating a CommitStatus

models/git/commit_status_test.go

@@ -5,11 +5,15 @@ package git_test
 
 import (
 	"testing"
+	"time"
 
 	"code.gitea.io/gitea/models/db"
 	git_model "code.gitea.io/gitea/models/git"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/structs"
 
 	"github.com/stretchr/testify/assert"
@@ -175,3 +179,55 @@ func Test_CalcCommitStatus(t *testing.T) {
 		assert.Equal(t, kase.expected, git_model.CalcCommitStatus(kase.statuses))
 	}
 }
+
+func TestFindRepoRecentCommitStatusContexts(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	repo2 := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 2})
+	user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	gitRepo, err := gitrepo.OpenRepository(git.DefaultContext, repo2)
+	assert.NoError(t, err)
+	defer gitRepo.Close()
+
+	commit, err := gitRepo.GetBranchCommit(repo2.DefaultBranch)
+	assert.NoError(t, err)
+
+	defer func() {
+		_, err := db.DeleteByBean(db.DefaultContext, &git_model.CommitStatus{
+			RepoID:    repo2.ID,
+			CreatorID: user2.ID,
+			SHA:       commit.ID.String(),
+		})
+		assert.NoError(t, err)
+	}()
+
+	err = git_model.NewCommitStatus(db.DefaultContext, git_model.NewCommitStatusOptions{
+		Repo:    repo2,
+		Creator: user2,
+		SHA:     commit.ID,
+		CommitStatus: &git_model.CommitStatus{
+			State:     structs.CommitStatusFailure,
+			TargetURL: "https://example.com/tests/",
+			Context:   "compliance/lint-backend",
+		},
+	})
+	assert.NoError(t, err)
+
+	err = git_model.NewCommitStatus(db.DefaultContext, git_model.NewCommitStatusOptions{
+		Repo:    repo2,
+		Creator: user2,
+		SHA:     commit.ID,
+		CommitStatus: &git_model.CommitStatus{
+			State:     structs.CommitStatusSuccess,
+			TargetURL: "https://example.com/tests/",
+			Context:   "compliance/lint-backend",
+		},
+	})
+	assert.NoError(t, err)
+
+	contexts, err := git_model.FindRepoRecentCommitStatusContexts(db.DefaultContext, repo2.ID, time.Hour)
+	assert.NoError(t, err)
+	if assert.Len(t, contexts, 1) {
+		assert.Equal(t, "compliance/lint-backend", contexts[0])
+	}
+}