test: add a test to confirm the git-sync not pulling latest issue (#1146)

`git-sync` v4.1.0 couldn't pull the latest commit from a branch when the
branch has multiple remotes and the branch in different remotes are out
of sync.

This commit adds a test to confirm the behavior. A subsequent commit
will update git-sync to v4.2.0 to fix this issue.

Author: nan-yu

e2e/nomostest/git-server.go

@@ -23,6 +23,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/intstr"
 	"kpt.dev/configsync/e2e"
+	"kpt.dev/configsync/e2e/nomostest/gitproviders"
 	"kpt.dev/configsync/e2e/nomostest/testing"
 	"kpt.dev/configsync/pkg/core"
 	"kpt.dev/configsync/pkg/kinds"
@@ -32,7 +33,8 @@ import (
 
 const testGitNamespace = "config-management-system-test"
 const testGitServer = "test-git-server"
-const testGitServerImage = testing.TestInfraArtifactRegistry + "/git-server:v1.0.0"
+
+const testGitServerImage = testing.TestInfraArtifactRegistry + "/git-server:v1.0.0-68df304c"
 const testGitHTTPServer = "http-git-server"
 const testGitHTTPServerImage = testing.TestInfraArtifactRegistry + "/http-git-server:v1.0.0-b3b4984cd"
 
@@ -208,13 +210,19 @@ func InitGitRepos(nt *NT, repos ...types.NamespacedName) {
 	podName := pod.Name
 
 	for _, repo := range repos {
-		nt.MustKubectl("exec", "-n", testGitNamespace, podName, "-c", testGitServer, "--",
-			"git", "init", "--bare", "--shared", fmt.Sprintf("/git-server/repos/%s/%s", repo.Namespace, repo.Name))
+		nt.MustKubectl("exec", "-n", testGitNamespace, podName,
+			"-c", testGitServer, "--",
+			"git", "init", "--bare", "--shared",
+			// Use `main` as the initial branch so that `HEAD` can reference refs/heads/main
+			"--initial-branch="+gitproviders.MainBranch,
+			fmt.Sprintf("/git-server/repos/%s/%s", repo.Namespace, repo.Name))
 		// We set receive.denyNonFastforwards to allow force pushes for legacy test support (bats).  In the future we may
 		// need this support for testing GKE clusters since we will likely be re-using the cluster in that case.
 		// Alternatively, we could also run "rm -rf /git-server/repos/*" to clear out the state of the git server and
 		// re-initialize.
-		nt.MustKubectl("exec", "-n", testGitNamespace, podName, "-c", testGitServer, "--",
-			"git", "-C", fmt.Sprintf("/git-server/repos/%s", repo), "config", "receive.denyNonFastforwards", "false")
+		nt.MustKubectl("exec", "-n", testGitNamespace, podName,
+			"-c", testGitServer, "--",
+			"git", "-C", fmt.Sprintf("/git-server/repos/%s", repo),
+			"config", "receive.denyNonFastforwards", "false")
 	}
 }

e2e/testcases/git_sync_test.go

@@ -0,0 +1,77 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package e2e
+
+import (
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"kpt.dev/configsync/e2e/nomostest"
+	"kpt.dev/configsync/e2e/nomostest/gitproviders"
+	nomostesting "kpt.dev/configsync/e2e/nomostest/testing"
+	"kpt.dev/configsync/pkg/api/configmanagement"
+	"kpt.dev/configsync/pkg/api/configsync"
+	"kpt.dev/configsync/pkg/testing/fake"
+)
+
+func TestMultipleRemoteBranchesOutOfSync(t *testing.T) {
+	nt := nomostest.New(t, nomostesting.ACMController)
+
+	rs := fake.RootSyncObjectV1Beta1(configsync.RootSyncName)
+	if err := nt.KubeClient.Get(configsync.RootSyncName, configmanagement.ControllerNamespace, rs); err != nil {
+		nt.T.Fatal(err)
+	}
+	initialSyncedCommit := rs.Status.LastSyncedCommit
+
+	nt.T.Log("Create an extra remote tracking branch")
+	nt.Must(nt.RootRepos[configsync.RootSyncName].Push("HEAD:refs/remotes/upstream/main"))
+	nt.T.Cleanup(func() {
+		// Delete the remote tracking branch in the end so other subsequent tests
+		// can pull from the latest commit, instead of the HEAD of the remote.
+		nt.Must(nt.RootRepos[configsync.RootSyncName].Push(":refs/remotes/upstream/main"))
+	})
+
+	nt.T.Logf("Update the remote main branch by adding a test namespace")
+	nt.Must(nt.RootRepos[configsync.RootSyncName].Add("acme/namespaces/hello/ns.yaml", fake.NamespaceObject("hello")))
+	nt.Must(nt.RootRepos[configsync.RootSyncName].CommitAndPush("add Namespace"))
+
+	nt.T.Logf("Mitigation: set spec.git.branch to HEAD to pull the latest commit")
+	nomostest.SetGitBranch(nt, configsync.RootSyncName, "HEAD")
+	// WatchForAllSyncs validates RootSync's lastSyncedCommit is updated to the
+	// local HEAD with the DefaultRootSha1Fn function.
+	if err := nt.WatchForAllSyncs(); err != nil {
+		nt.T.Fatal(err)
+	}
+	if err := nt.Validate("hello", "", &corev1.Namespace{}); err != nil {
+		nt.T.Fatal(err)
+	}
+
+	// Apply the mitigation first to validate Config Sync couldn't pull the latest commit.
+	nt.T.Logf("Verify the issue exist with the default branch and revision")
+	nomostest.SetGitBranch(nt, configsync.RootSyncName, gitproviders.MainBranch)
+	if err := nt.WatchForAllSyncs(nomostest.WithRootSha1Func(
+		// DefaultRootSha1Fn returns the hash with `git rev-parse HEAD`, which is
+		// different from `git ls-remote ...`
+		// So, overwrite the root hash with the initial lastSyncedCommit.
+		func(_ *nomostest.NT, _ types.NamespacedName) (string, error) {
+			return initialSyncedCommit, nil
+		})); err != nil {
+		nt.T.Fatal(err)
+	}
+	if err := nt.ValidateNotFound("hello", "", &corev1.Namespace{}); err != nil {
+		nt.T.Fatal(err)
+	}
+}