Implement FindBranch RPC

Closes gitaly#501

4 files changed, 123 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7cf30bbef..1efd299a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@ UNRELEASED
 
 - Terminate commands when their context cancels
   https://gitlab.com/gitlab-org/gitaly/merge_requests/318
+- Implement FindBranch RPC
+  https://gitlab.com/gitlab-org/gitaly/merge_requests/315
 - Implement {Create,Delete}Branch RPCs
   https://gitlab.com/gitlab-org/gitaly/merge_requests/311
 
diff --git a/internal/service/ref/branches.go b/internal/service/ref/branches.go
index 06724df86..5b4e12e4f 100644
--- a/internal/service/ref/branches.go
+++ b/internal/service/ref/branches.go
@@ -37,5 +37,15 @@ func (s *server) DeleteBranch(ctx context.Context, req *pb.DeleteBranchRequest)
 }
 
 func (s *server) FindBranch(ctx context.Context, req *pb.FindBranchRequest) (*pb.FindBranchResponse, error) {
-	return nil, nil
+	client, err := rubyserver.RefServiceClient(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	clientCtx, err := rubyserver.SetHeaders(ctx, req.GetRepository())
+	if err != nil {
+		return nil, err
+	}
+
+	return client.FindBranch(clientCtx, req)
 }
diff --git a/internal/service/ref/branches_test.go b/internal/service/ref/branches_test.go
index 1b6c21360..585f3b467 100644
--- a/internal/service/ref/branches_test.go
+++ b/internal/service/ref/branches_test.go
@@ -208,3 +208,99 @@ func TestFailedDeleteBranchRequest(t *testing.T) {
 		})
 	}
 }
+
+func TestSuccessfulFindBranchRequest(t *testing.T) {
+	server := runRefServiceServer(t)
+	defer server.Stop()
+
+	client, conn := newRefClient(t)
+	defer conn.Close()
+
+	branchNameInput := "master"
+	branchTarget, err := log.GetCommit(context.Background(), testRepo, branchNameInput, "")
+	require.NoError(t, err)
+
+	branch := &pb.Branch{
+		Name:         []byte(branchNameInput),
+		TargetCommit: branchTarget,
+	}
+
+	testCases := []struct {
+		desc           string
+		branchName     string
+		expectedBranch *pb.Branch
+	}{
+		{
+			desc:           "regular branch name",
+			branchName:     branchNameInput,
+			expectedBranch: branch,
+		},
+		{
+			desc:           "absolute reference path",
+			branchName:     "refs/heads/" + branchNameInput,
+			expectedBranch: branch,
+		},
+		{
+			desc:           "heads path",
+			branchName:     "heads/" + branchNameInput,
+			expectedBranch: branch,
+		},
+		{
+			desc:       "non-existent branch",
+			branchName: "i-do-not-exist-on-this-repo",
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.desc, func(t *testing.T) {
+			request := &pb.FindBranchRequest{
+				Repository: testRepo,
+				Name:       []byte(testCase.branchName),
+			}
+
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			response, err := client.FindBranch(ctx, request)
+
+			require.NoError(t, err)
+			require.Equal(t, testCase.expectedBranch, response.Branch, "mismatched branches")
+		})
+	}
+}
+
+func TestFailedFindBranchRequest(t *testing.T) {
+	server := runRefServiceServer(t)
+	defer server.Stop()
+
+	client, conn := newRefClient(t)
+	defer conn.Close()
+
+	testCases := []struct {
+		desc       string
+		branchName string
+		code       codes.Code
+	}{
+		{
+			desc:       "empty branch name",
+			branchName: "",
+			code:       codes.InvalidArgument,
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.desc, func(t *testing.T) {
+
+			request := &pb.FindBranchRequest{
+				Repository: testRepo,
+				Name:       []byte(testCase.branchName),
+			}
+
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			_, err := client.FindBranch(ctx, request)
+			testhelper.AssertGrpcError(t, err, testCase.code, "")
+		})
+	}
+}
diff --git a/ruby/lib/gitaly_server/ref_service.rb b/ruby/lib/gitaly_server/ref_service.rb
index 158a7f803..7abed4da9 100644
--- a/ruby/lib/gitaly_server/ref_service.rb
+++ b/ruby/lib/gitaly_server/ref_service.rb
@@ -41,5 +41,19 @@ module GitalyServer
     rescue Rugged::ReferenceError => e
       raise GRPC::Internal.new(e.to_s)
     end
+
+    def find_branch(request, _call)
+      branch_name = request.name
+      raise GRPC::InvalidArgument.new("empty Name") if branch_name.empty?
+
+      repo = Gitlab::Git::Repository.from_call(_call)
+      rugged_branch = repo.find_branch(branch_name)
+      gitaly_branch = Gitaly::Branch.new(
+        name: rugged_branch.name.b,
+        target_commit: gitaly_commit_from_rugged(rugged_branch.dereferenced_target.raw_commit),
+      ) unless rugged_branch.nil?
+
+      Gitaly::FindBranchResponse.new(branch: gitaly_branch)
+    end
   end
 end