Merge branch 'smh-forced-reference-updates' into 'master'

Allow forcing reference updates in TransactionManager

Closes #5141

See merge request https://gitlab.com/gitlab-org/gitaly/-/merge_requests/5800

Merged-by: Will Chandler <wchandler@gitlab.com>
Approved-by: Toon Claes <toon@gitlab.com>
Approved-by: Will Chandler <wchandler@gitlab.com>
Co-authored-by: Sami Hiltunen <shiltunen@gitlab.com>

2 files changed, 111 insertions, 21 deletions

diff --git a/internal/gitaly/transaction_manager.go b/internal/gitaly/transaction_manager.go
index 4fecda296..4e2060dcf 100644
--- a/internal/gitaly/transaction_manager.go
+++ b/internal/gitaly/transaction_manager.go
@@ -93,6 +93,9 @@ func (index LogIndex) String() string {
 
 // ReferenceUpdate describes the state of a reference's old and new tip in an update.
 type ReferenceUpdate struct {
+	// Force indicates this is a forced reference update. If set, the reference is pointed
+	// to the new value regardless of the old value.
+	Force bool
 	// OldOID is the old OID the reference is expected to point to prior to updating it.
 	// If the reference does not point to the old value, the reference verification fails.
 	OldOID git.ObjectID
@@ -1027,7 +1030,7 @@ func packFilePathForLogIndex(repoPath string, index LogIndex) string {
 // It returns the write-ahead log entry for the transaction if it was successfully verified.
 func (mgr *TransactionManager) verifyReferences(ctx context.Context, transaction *Transaction) ([]*gitalypb.LogEntry_ReferenceUpdate, error) {
 	var referenceUpdates []*gitalypb.LogEntry_ReferenceUpdate
-	for referenceName, tips := range transaction.referenceUpdates {
+	for referenceName, update := range transaction.referenceUpdates {
 		// 'git update-ref' doesn't ensure the loose references end up in the
 		// refs directory so we enforce that here.
 		if !strings.HasPrefix(referenceName.String(), "refs/") {
@@ -1043,33 +1046,35 @@ func (mgr *TransactionManager) verifyReferences(ctx context.Context, transaction
 			}
 		}
 
-		actualOldTip, err := transaction.stagingRepository.ResolveRevision(ctx, referenceName.Revision())
-		if errors.Is(err, git.ErrReferenceNotFound) {
-			objectHash, err := transaction.stagingRepository.ObjectHash(ctx)
-			if err != nil {
-				return nil, fmt.Errorf("object hash: %w", err)
-			}
-
-			actualOldTip = objectHash.ZeroOID
-		} else if err != nil {
-			return nil, fmt.Errorf("resolve revision: %w", err)
-		}
+		if !update.Force {
+			actualOldTip, err := transaction.stagingRepository.ResolveRevision(ctx, referenceName.Revision())
+			if errors.Is(err, git.ErrReferenceNotFound) {
+				objectHash, err := transaction.stagingRepository.ObjectHash(ctx)
+				if err != nil {
+					return nil, fmt.Errorf("object hash: %w", err)
+				}
 
-		if tips.OldOID != actualOldTip {
-			if transaction.skipVerificationFailures {
-				continue
+				actualOldTip = objectHash.ZeroOID
+			} else if err != nil {
+				return nil, fmt.Errorf("resolve revision: %w", err)
 			}
 
-			return nil, ReferenceVerificationError{
-				ReferenceName: referenceName,
-				ExpectedOID:   tips.OldOID,
-				ActualOID:     actualOldTip,
+			if update.OldOID != actualOldTip {
+				if transaction.skipVerificationFailures {
+					continue
+				}
+
+				return nil, ReferenceVerificationError{
+					ReferenceName: referenceName,
+					ExpectedOID:   update.OldOID,
+					ActualOID:     actualOldTip,
+				}
 			}
 		}
 
 		referenceUpdates = append(referenceUpdates, &gitalypb.LogEntry_ReferenceUpdate{
 			ReferenceName: []byte(referenceName),
-			NewOid:        []byte(tips.NewOID),
+			NewOid:        []byte(update.NewOID),
 		})
 	}
 
diff --git a/internal/gitaly/transaction_manager_test.go b/internal/gitaly/transaction_manager_test.go
index b8fb7c073..92eb248d3 100644
--- a/internal/gitaly/transaction_manager_test.go
+++ b/internal/gitaly/transaction_manager_test.go
@@ -2629,6 +2629,91 @@ func TestTransactionManager(t *testing.T) {
 				RepositoryDoesntExist: true,
 			},
 		},
+		{
+			desc: "forced reference creation succeeds",
+			steps: steps{
+				StartManager{},
+				Begin{},
+				Commit{
+					ReferenceUpdates: ReferenceUpdates{
+						"refs/heads/main": {Force: true, NewOID: setup.Commits.First.OID},
+					},
+				},
+			},
+			expectedState: StateAssertion{
+				DefaultBranch: "refs/heads/main",
+				References:    []git.Reference{{Name: "refs/heads/main", Target: setup.Commits.First.OID.String()}},
+				Database: DatabaseState{
+					string(keyAppliedLogIndex(relativePath)): LogIndex(1).toProto(),
+				},
+			},
+		},
+		{
+			desc: "forced reference update succeeds",
+			steps: steps{
+				StartManager{},
+				Begin{
+					TransactionID: 1,
+				},
+				Commit{
+					TransactionID: 1,
+					ReferenceUpdates: ReferenceUpdates{
+						"refs/heads/main": {OldOID: setup.ObjectHash.ZeroOID, NewOID: setup.Commits.First.OID},
+					},
+				},
+				Begin{
+					TransactionID: 2,
+					ExpectedSnapshot: Snapshot{
+						ReadIndex: 1,
+					},
+				},
+				Commit{
+					TransactionID: 2,
+					ReferenceUpdates: ReferenceUpdates{
+						"refs/heads/main": {Force: true, NewOID: setup.Commits.Second.OID},
+					},
+				},
+			},
+			expectedState: StateAssertion{
+				DefaultBranch: "refs/heads/main",
+				References:    []git.Reference{{Name: "refs/heads/main", Target: setup.Commits.Second.OID.String()}},
+				Database: DatabaseState{
+					string(keyAppliedLogIndex(relativePath)): LogIndex(2).toProto(),
+				},
+			},
+		},
+		{
+			desc: "forced reference deletion succeeds",
+			steps: steps{
+				StartManager{},
+				Begin{
+					TransactionID: 1,
+				},
+				Commit{
+					TransactionID: 1,
+					ReferenceUpdates: ReferenceUpdates{
+						"refs/heads/main": {OldOID: setup.ObjectHash.ZeroOID, NewOID: setup.Commits.First.OID},
+					},
+				},
+				Begin{
+					TransactionID: 2,
+					ExpectedSnapshot: Snapshot{
+						ReadIndex: 1,
+					},
+				},
+				Commit{
+					TransactionID: 2,
+					ReferenceUpdates: ReferenceUpdates{
+						"refs/heads/main": {Force: true, NewOID: setup.ObjectHash.ZeroOID},
+					},
+				},
+			},
+			expectedState: StateAssertion{
+				Database: DatabaseState{
+					string(keyAppliedLogIndex(relativePath)): LogIndex(2).toProto(),
+				},
+			},
+		},
 	}
 
 	type invalidReferenceTestCase struct {
@@ -2657,7 +2742,7 @@ func TestTransactionManager(t *testing.T) {
 				Begin{},
 				Commit{
 					ReferenceUpdates: ReferenceUpdates{
-						tc.referenceName: {OldOID: setup.ObjectHash.ZeroOID, NewOID: setup.Commits.First.OID},
+						tc.referenceName: {Force: true, NewOID: setup.Commits.First.OID},
 					},
 					ExpectedError: err,
 				},