remoterepo: Implement `GetDefaultBranch()`

We have an ad-hoc implementation of `GetDefaultBranch()` for remote
repositories in the `FetchInternalRemote()` RPC implementation. Given
that this RPC call simply maps to `localrepo.GetDefaultBranch()`, it
makes sense to pull up the implementation into the remoterepo interface
to make it generally available.

Implement `remoterepo.GetDefaultBranch()` and move tests of this
function from localrepo-specific tests into the shared test suite.

5 files changed, 117 insertions, 84 deletions

diff --git a/internal/git/gittest/repository_suite.go b/internal/git/gittest/repository_suite.go
index 7da568cc8..2da7d8af8 100644
--- a/internal/git/gittest/repository_suite.go
+++ b/internal/git/gittest/repository_suite.go
@@ -25,6 +25,10 @@ func TestRepository(t *testing.T, cfg config.Cfg, getRepository func(testing.TB,
 			desc: "HasBranches",
 			test: testRepositoryHasBranches,
 		},
+		{
+			desc: "GetDefaultBranch",
+			test: testRepositoryGetDefaultBranch,
+		},
 	} {
 		t.Run(tc.desc, func(t *testing.T) {
 			tc.test(t, cfg, getRepository)
@@ -107,3 +111,93 @@ func testRepositoryHasBranches(t *testing.T, cfg config.Cfg, getRepository func(
 	require.NoError(t, err)
 	require.True(t, hasBranches)
 }
+
+func testRepositoryGetDefaultBranch(t *testing.T, cfg config.Cfg, getRepository func(testing.TB, *gitalypb.Repository) git.Repository) {
+	const testOID = "1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"
+
+	for _, tc := range []struct {
+		desc         string
+		repo         func(t *testing.T) git.Repository
+		expectedName git.ReferenceName
+	}{
+		{
+			desc: "default ref",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, repoPath := InitRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("main"))
+				return repo
+			},
+			expectedName: git.ReferenceName(git.DefaultRef),
+		},
+		{
+			desc: "legacy default ref",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, repoPath := InitRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("master"))
+				return repo
+			},
+			expectedName: git.ReferenceName(git.LegacyDefaultRef),
+		},
+		{
+			desc: "no branches",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, _ := InitRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				return repo
+			},
+		},
+		{
+			desc: "one branch",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, repoPath := InitRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				return repo
+			},
+			expectedName: git.NewReferenceNameFromBranchName("apple"),
+		},
+		{
+			desc: "no default branches",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, repoPath := InitRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				oid := WriteCommit(t, cfg, repoPath, WithParents(), WithBranch("apple"))
+				WriteCommit(t, cfg, repoPath, WithParents(oid), WithBranch("banana"))
+				return repo
+			},
+			expectedName: git.NewReferenceNameFromBranchName("apple"),
+		},
+		{
+			desc: "test repo default",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, _ := CloneRepo(t, cfg, cfg.Storages[0])
+				return getRepository(t, repoProto)
+			},
+			expectedName: git.ReferenceName(git.LegacyDefaultRef),
+		},
+		{
+			desc: "test repo HEAD set",
+			repo: func(t *testing.T) git.Repository {
+				repoProto, repoPath := CloneRepo(t, cfg, cfg.Storages[0])
+				repo := getRepository(t, repoProto)
+				Exec(t, cfg, "-C", repoPath, "update-ref", "refs/heads/feature", testOID)
+				Exec(t, cfg, "-C", repoPath, "symbolic-ref", "HEAD", "refs/heads/feature")
+				return repo
+			},
+			expectedName: git.NewReferenceNameFromBranchName("feature"),
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			ctx, cancel := testhelper.Context()
+			defer cancel()
+
+			name, err := tc.repo(t).GetDefaultBranch(ctx)
+			require.NoError(t, err)
+			require.Equal(t, tc.expectedName, name)
+		})
+	}
+}
diff --git a/internal/git/localrepo/refs_test.go b/internal/git/localrepo/refs_test.go
index 069073e47..3d3fdcd32 100644
--- a/internal/git/localrepo/refs_test.go
+++ b/internal/git/localrepo/refs_test.go
@@ -453,87 +453,3 @@ func TestRepo_UpdateRef(t *testing.T) {
 		})
 	}
 }
-
-func TestGetDefaultBranch(t *testing.T) {
-	const testOID = "1a0b36b3cdad1d2ee32457c102a8c0b7056fa863"
-
-	for _, tc := range []struct {
-		desc         string
-		repo         func(t *testing.T) *Repo
-		expectedName git.ReferenceName
-	}{
-		{
-			desc: "default ref",
-			repo: func(t *testing.T) *Repo {
-				repo, repoPath := setupRepo(t, true)
-				oid := gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(), gittest.WithBranch("apple"))
-				gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(oid), gittest.WithBranch("main"))
-				return repo
-			},
-			expectedName: git.ReferenceName(git.DefaultRef),
-		},
-		{
-			desc: "legacy default ref",
-			repo: func(t *testing.T) *Repo {
-				repo, repoPath := setupRepo(t, true)
-				oid := gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(), gittest.WithBranch("apple"))
-				gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(oid), gittest.WithBranch("master"))
-				return repo
-			},
-			expectedName: git.ReferenceName(git.LegacyDefaultRef),
-		},
-		{
-			desc: "no branches",
-			repo: func(t *testing.T) *Repo {
-				repo, _ := setupRepo(t, true)
-				return repo
-			},
-		},
-		{
-			desc: "one branch",
-			repo: func(t *testing.T) *Repo {
-				repo, repoPath := setupRepo(t, true)
-				gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(), gittest.WithBranch("apple"))
-				return repo
-			},
-			expectedName: git.NewReferenceNameFromBranchName("apple"),
-		},
-		{
-			desc: "no default branches",
-			repo: func(t *testing.T) *Repo {
-				repo, repoPath := setupRepo(t, true)
-				oid := gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(), gittest.WithBranch("apple"))
-				gittest.WriteCommit(t, repo.cfg, repoPath, gittest.WithParents(oid), gittest.WithBranch("banana"))
-				return repo
-			},
-			expectedName: git.NewReferenceNameFromBranchName("apple"),
-		},
-		{
-			desc: "test repo default",
-			repo: func(t *testing.T) *Repo {
-				repo, _ := setupRepo(t, false)
-				return repo
-			},
-			expectedName: git.ReferenceName(git.LegacyDefaultRef),
-		},
-		{
-			desc: "test repo HEAD set",
-			repo: func(t *testing.T) *Repo {
-				repo, repoPath := setupRepo(t, false)
-				gittest.Exec(t, repo.cfg, "-C", repoPath, "update-ref", "refs/heads/feature", testOID)
-				gittest.Exec(t, repo.cfg, "-C", repoPath, "symbolic-ref", "HEAD", "refs/heads/feature")
-				return repo
-			},
-			expectedName: git.NewReferenceNameFromBranchName("feature"),
-		},
-	} {
-		t.Run(tc.desc, func(t *testing.T) {
-			ctx, cancel := testhelper.Context()
-			defer cancel()
-
-			name, err := tc.repo(t).GetDefaultBranch(ctx)
-			require.NoError(t, err)
-			require.Equal(t, tc.expectedName, name)
-		})
-	}
-}
diff --git a/internal/git/remoterepo/repository.go b/internal/git/remoterepo/repository.go
index 69fa197f4..c31248f65 100644
--- a/internal/git/remoterepo/repository.go
+++ b/internal/git/remoterepo/repository.go
@@ -70,3 +70,16 @@ func (rr *Repo) HasBranches(ctx context.Context) (bool, error) {
 
 	return resp.Value, nil
 }
+
+// GetDefaultBranch returns the default branch for the remote repository. It does so by invoking
+// `FindDefaultBranchName()`, which itself is a wrapper around `localrepo.GetDefaultBranch()`.
+// Semantics of this function thus match the localrepo semantics.
+func (rr *Repo) GetDefaultBranch(ctx context.Context) (git.ReferenceName, error) {
+	resp, err := gitalypb.NewRefServiceClient(rr.conn).FindDefaultBranchName(
+		ctx, &gitalypb.FindDefaultBranchNameRequest{Repository: rr.Repository})
+	if err != nil {
+		return "", err
+	}
+
+	return git.ReferenceName(resp.Name), nil
+}
diff --git a/internal/git/remoterepo/repository_test.go b/internal/git/remoterepo/repository_test.go
index b209ef79d..ddc63fb11 100644
--- a/internal/git/remoterepo/repository_test.go
+++ b/internal/git/remoterepo/repository_test.go
@@ -10,6 +10,7 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v14/internal/git/remoterepo"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/service"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/service/commit"
+	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/service/ref"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/service/repository"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/storage"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/metadata"
@@ -39,6 +40,13 @@ func TestRepository(t *testing.T) {
 			deps.GetLinguist(),
 			deps.GetCatfileCache(),
 		))
+		gitalypb.RegisterRefServiceServer(srv, ref.NewServer(
+			deps.GetCfg(),
+			deps.GetLocator(),
+			deps.GetGitCmdFactory(),
+			deps.GetTxManager(),
+			deps.GetCatfileCache(),
+		))
 	})
 
 	ctx, cancel := testhelper.Context()
diff --git a/internal/git/repository.go b/internal/git/repository.go
index e5f5b25d5..2bdb6daef 100644
--- a/internal/git/repository.go
+++ b/internal/git/repository.go
@@ -44,6 +44,8 @@ type Repository interface {
 	ResolveRevision(ctx context.Context, revision Revision) (ObjectID, error)
 	// HasBranches returns whether the repository has branches.
 	HasBranches(ctx context.Context) (bool, error)
+	// GetDefaultBranch returns the default branch of the repository.
+	GetDefaultBranch(ctx context.Context) (ReferenceName, error)
 }
 
 // RepositoryExecutor is an interface which allows execution of Git commands in a specific