Fix bug when pushing into different branches

Changes replacing go-git with git2go introduced a bug
in which pushes into new branches squashes all commits
into one.

xref: fluxcd#324
Signed-off-by: Paulo Gomes <[email protected]>

controllers/git_test.go

@@ -134,6 +134,9 @@ func TestPushRejected(t *testing.T) {
 
 	repoURL := gitServer.HTTPAddressWithCredentials() + "/appconfig.git"
 	repo, err := clone(repoURL, "origin", "main")
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	// This is here to guard against push in general being broken
 	err = push(context.TODO(), repo.Workdir(), "main", repoAccess{

controllers/imageupdateautomation_controller.go

@@ -292,10 +292,7 @@ func (r *ImageUpdateAutomationReconciler) Reconcile(ctx context.Context, req ctr
 		// Use the git operations timeout for the repo.
 		fetchCtx, cancel := context.WithTimeout(ctx, origin.Spec.Timeout.Duration)
 		defer cancel()
-		if err := fetch(fetchCtx, tmp, pushBranch, access); err != nil && err != errRemoteBranchMissing {
-			return failWithError(err)
-		}
-		if err = switchBranch(repo, pushBranch); err != nil {
+		if err := switchToBranch(repo, fetchCtx, pushBranch, access); err != nil && err != errRemoteBranchMissing {
 			return failWithError(err)
 		}
 	}
@@ -556,25 +553,6 @@ func cloneInto(ctx context.Context, access repoAccess, ref *sourcev1.GitReposito
 	return libgit2.OpenRepository(path)
 }
 
-// switchBranch switches the repo from the current branch to the
-// branch given. If the branch does not exist, it is created using the
-// head as the starting point.
-func switchBranch(repo *libgit2.Repository, pushBranch string) error {
-	if err := repo.SetHead(fmt.Sprintf("refs/heads/%s", pushBranch)); err != nil {
-		head, err := headCommit(repo)
-		if err != nil {
-			return err
-		}
-		defer head.Free()
-
-		branch, err := repo.CreateBranch(pushBranch, head, false)
-		defer branch.Free()
-		return err
-	}
-
-	return nil
-}
-
 func headCommit(repo *libgit2.Repository) (*libgit2.Commit, error) {
 	head, err := repo.Head()
 	if err != nil {
@@ -748,35 +726,65 @@ func (r *ImageUpdateAutomationReconciler) getSigningEntity(ctx context.Context,
 
 var errRemoteBranchMissing = errors.New("remote branch missing")
 
-// fetch gets the remote branch given and updates the local branch
-// head of the same name, so it can be switched to. If the fetch
-// completes, it returns nil; if the remote branch is missing, it
-// returns errRemoteBranchMissing (this is to work in sympathy with
-// `switchBranch`, which will create the branch if it doesn't
-// exist). For any other problem it will return the error.
-func fetch(ctx context.Context, path string, branch string, access repoAccess) error {
-	refspec := fmt.Sprintf("refs/heads/%s:refs/heads/%s", branch, branch)
-	repo, err := libgit2.OpenRepository(path)
-	if err != nil {
+// switchToBranch switches to a branch after fetching latest from upstream.
+// If the branch does not exist, it is created using the head as the starting point.
+func switchToBranch(repo *libgit2.Repository, ctx context.Context, branch string, access repoAccess) error {
+	checkoutOpts := &libgit2.CheckoutOpts{
+		// the remote branch should take precedence if it exists at this point in time.
+		Strategy: libgit2.CheckoutForce,
+	}
+
+	branchRef := fmt.Sprintf("origin/%s", branch)
+	remoteBranch, err := repo.LookupBranch(branchRef, libgit2.BranchRemote)
+	if err != nil && !libgit2.IsErrorCode(err, libgit2.ErrorCodeNotFound) {
 		return err
 	}
-	defer repo.Free()
-	origin, err := repo.Remotes.Lookup(originRemote)
+	if remoteBranch != nil {
+		defer remoteBranch.Free()
+	}
+	err = nil
+
+	var commit *libgit2.Commit
+	// tries to get tip commit from remote branch, if it exists.
+	// otherwise gets the commit that local head is pointing to.
+	if remoteBranch != nil {
+		commit, err = repo.LookupCommit(remoteBranch.Target())
+	} else {
+		head, err := repo.Head()
+		if err != nil {
+			return fmt.Errorf("cannot get repo head: %w", err)
+		}
+		commit, err = repo.LookupCommit(head.Target())
+	}
 	if err != nil {
-		return err
+		return fmt.Errorf("cannot find the head commit: %w", err)
 	}
-	defer origin.Free()
-	err = origin.Fetch(
-		[]string{refspec},
-		&libgit2.FetchOptions{
-			RemoteCallbacks: access.remoteCallbacks(ctx),
-			ProxyOptions:    libgit2.ProxyOptions{Type: libgit2.ProxyTypeAuto},
-		}, "",
-	)
-	if err != nil && libgit2.IsErrorCode(err, libgit2.ErrorCodeNotFound) {
-		return errRemoteBranchMissing
+	defer commit.Free()
+
+	localBranch, err := repo.LookupBranch(branch, libgit2.BranchLocal)
+	if err != nil && !libgit2.IsErrorCode(err, libgit2.ErrorCodeNotFound) {
+		return fmt.Errorf("cannot lookup branch %q: %w", branch, err)
+	}
+	if localBranch == nil {
+		localBranch, err = repo.CreateBranch(branch, commit, false)
 	}
-	return err
+	if localBranch == nil {
+		return fmt.Errorf("cannot create local branch %q: %w", branch, err)
+	}
+	defer localBranch.Free()
+
+	tree, err := repo.LookupTree(commit.TreeId())
+	if err != nil {
+		return fmt.Errorf("cannot lookup tree for branch %q: %w", branch, err)
+	}
+	defer tree.Free()
+
+	err = repo.CheckoutTree(tree, checkoutOpts)
+	if err != nil {
+		return fmt.Errorf("cannot checkout tree for branch %q: %w", branch, err)
+	}
+
+	return repo.SetHead("refs/heads/" + branch)
 }
 
 // push pushes the branch given to the origin using the git library

controllers/update_test.go

@@ -990,6 +990,10 @@ Images:
 				})
 
 				It("creates and pushes the push branch", func() {
+					initialHead, err := headFromBranch(localRepo, branch)
+					Expect(err).ToNot(HaveOccurred())
+					defer initialHead.Free()
+
 					// pull the head commit we just pushed, so it's not
 					// considered a new commit when checking for a commit
 					// made by automation.
@@ -1003,6 +1007,13 @@ Images:
 					Expect(err).ToNot(HaveOccurred())
 					defer commit.Free()
 					Expect(commit.Message()).To(Equal(commitMessage))
+
+					// previous commits should still exist in the tree
+					// checks for regression in which the new branch had only the new commit.
+					oldCommit, err := localRepo.LookupCommit(initialHead.Id())
+					Expect(err).ToNot(HaveOccurred())
+					Expect(oldCommit).ToNot(BeNil())
+					defer commit.Free()
 				})
 
 				It("pushes another commit to the existing push branch", func() {
@@ -1731,6 +1742,10 @@ func rebase(repo *git2go.Repository, sourceBranch, targetBranch string) (*git2go
 
 		// Check operation index is correct
 		rebaseOperationIndex, err = rebase.CurrentOperationIndex()
+		if err != nil {
+			return nil, err
+		}
+
 		if int(rebaseOperationIndex) != op {
 			return nil, errors.New("Bad operation index")
 		}