detect force push (#856)

app/api/controller/githook/controller.go

@@ -25,6 +25,7 @@ import (
 	"github.com/harness/gitness/app/services/protection"
 	"github.com/harness/gitness/app/store"
 	"github.com/harness/gitness/app/url"
+	"github.com/harness/gitness/git"
 	"github.com/harness/gitness/types"
 	"github.com/harness/gitness/types/enum"
 )
@@ -57,6 +58,7 @@ type Controller struct {
 	principalStore    store.PrincipalStore
 	repoStore         store.RepoStore
 	gitReporter       *eventsgit.Reporter
+	git               git.Interface
 	pullreqStore      store.PullReqStore
 	urlProvider       url.Provider
 	protectionManager *protection.Manager
@@ -67,6 +69,7 @@ func NewController(
 	principalStore store.PrincipalStore,
 	repoStore store.RepoStore,
 	gitReporter *eventsgit.Reporter,
+	git git.Interface,
 	pullreqStore store.PullReqStore,
 	urlProvider url.Provider,
 	protectionManager *protection.Manager,
@@ -76,6 +79,7 @@ func NewController(
 		principalStore:    principalStore,
 		repoStore:         repoStore,
 		gitReporter:       gitReporter,
+		git:               git,
 		pullreqStore:      pullreqStore,
 		urlProvider:       urlProvider,
 		protectionManager: protectionManager,

app/api/controller/githook/post_receive.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/harness/gitness/app/auth"
 	events "github.com/harness/gitness/app/events/git"
+	"github.com/harness/gitness/git"
 	"github.com/harness/gitness/githook"
 	"github.com/harness/gitness/types"
 	"github.com/harness/gitness/types/enum"
@@ -53,7 +54,7 @@ func (c *Controller) PostReceive(
 	}
 
 	// report ref events (best effort)
-	c.reportReferenceEvents(ctx, repoID, principalID, in)
+	c.reportReferenceEvents(ctx, repo, principalID, in)
 
 	// create output object and have following messages fill its messages
 	out := &githook.Output{}
@@ -69,16 +70,16 @@ func (c *Controller) PostReceive(
 // TODO: in the future we might want to think about propagating errors so user is aware of events not being triggered.
 func (c *Controller) reportReferenceEvents(
 	ctx context.Context,
-	repoID int64,
+	repo *types.Repository,
 	principalID int64,
 	in githook.PostReceiveInput,
 ) {
 	for _, refUpdate := range in.RefUpdates {
 		switch {
 		case strings.HasPrefix(refUpdate.Ref, gitReferenceNamePrefixBranch):
-			c.reportBranchEvent(ctx, repoID, principalID, refUpdate)
+			c.reportBranchEvent(ctx, repo, principalID, refUpdate)
 		case strings.HasPrefix(refUpdate.Ref, gitReferenceNamePrefixTag):
-			c.reportTagEvent(ctx, repoID, principalID, refUpdate)
+			c.reportTagEvent(ctx, repo, principalID, refUpdate)
 		default:
 			// Ignore any other references in post-receive
 		}
@@ -87,61 +88,75 @@ func (c *Controller) reportReferenceEvents(
 
 func (c *Controller) reportBranchEvent(
 	ctx context.Context,
-	repoID int64,
+	repo *types.Repository,
 	principalID int64,
 	branchUpdate githook.ReferenceUpdate,
 ) {
 	switch {
 	case branchUpdate.Old == types.NilSHA:
 		c.gitReporter.BranchCreated(ctx, &events.BranchCreatedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         branchUpdate.Ref,
 			SHA:         branchUpdate.New,
 		})
 	case branchUpdate.New == types.NilSHA:
 		c.gitReporter.BranchDeleted(ctx, &events.BranchDeletedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         branchUpdate.Ref,
 			SHA:         branchUpdate.Old,
 		})
 	default:
+		result, err := c.git.IsAncestor(ctx, git.IsAncestorParams{
+			ReadParams:          git.ReadParams{RepoUID: repo.GitUID},
+			AncestorCommitSHA:   branchUpdate.Old,
+			DescendantCommitSHA: branchUpdate.New,
+		})
+		if err != nil {
+			log.Ctx(ctx).Err(err).
+				Str("ref", branchUpdate.Ref).
+				Msg("failed to check ancestor")
+		}
+		// In case of an error consider this a forced update. In post-update the branch has already been updated,
+		// so there's less harm in declaring the update as forced. A force update event might trigger some additional
+		// operations that aren't required for ordinary updates (force pushes alter the commit history of a branch).
+		forced := err != nil || !result.Ancestor
 		c.gitReporter.BranchUpdated(ctx, &events.BranchUpdatedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         branchUpdate.Ref,
 			OldSHA:      branchUpdate.Old,
 			NewSHA:      branchUpdate.New,
-			Forced:      false, // TODO: data not available yet
+			Forced:      forced,
 		})
 	}
 }
 
 func (c *Controller) reportTagEvent(
 	ctx context.Context,
-	repoID int64,
+	repo *types.Repository,
 	principalID int64,
 	tagUpdate githook.ReferenceUpdate,
 ) {
 	switch {
 	case tagUpdate.Old == types.NilSHA:
 		c.gitReporter.TagCreated(ctx, &events.TagCreatedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         tagUpdate.Ref,
 			SHA:         tagUpdate.New,
 		})
 	case tagUpdate.New == types.NilSHA:
 		c.gitReporter.TagDeleted(ctx, &events.TagDeletedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         tagUpdate.Ref,
 			SHA:         tagUpdate.Old,
 		})
 	default:
 		c.gitReporter.TagUpdated(ctx, &events.TagUpdatedPayload{
-			RepoID:      repoID,
+			RepoID:      repo.ID,
 			PrincipalID: principalID,
 			Ref:         tagUpdate.Ref,
 			OldSHA:      tagUpdate.Old,

app/api/controller/githook/wire.go

@@ -20,6 +20,7 @@ import (
 	"github.com/harness/gitness/app/services/protection"
 	"github.com/harness/gitness/app/store"
 	"github.com/harness/gitness/app/url"
+	"github.com/harness/gitness/git"
 
 	"github.com/google/wire"
 )
@@ -34,6 +35,7 @@ func ProvideController(
 	principalStore store.PrincipalStore,
 	repoStore store.RepoStore,
 	gitReporter *eventsgit.Reporter,
+	git git.Interface,
 	pullreqStore store.PullReqStore,
 	urlProvider url.Provider,
 	protectionManager *protection.Manager,
@@ -43,6 +45,7 @@ func ProvideController(
 		principalStore,
 		repoStore,
 		gitReporter,
+		git,
 		pullreqStore,
 		urlProvider,
 		protectionManager)

cmd/gitness/wire_gen.go

@@ -245,7 +245,7 @@ func initSystem(ctx context.Context, config *types.Config) (*server.System, erro
 	if err != nil {
 		return nil, err
 	}
-	githookController := githook.ProvideController(authorizer, principalStore, repoStore, reporter2, pullReqStore, provider, protectionManager)
+	githookController := githook.ProvideController(authorizer, principalStore, repoStore, reporter2, gitInterface, pullReqStore, provider, protectionManager)
 	serviceaccountController := serviceaccount.NewController(principalUID, authorizer, principalStore, spaceStore, repoStore, tokenStore)
 	principalController := principal.ProvideController(principalStore)
 	checkController := check2.ProvideController(transactor, authorizer, repoStore, checkStore, gitInterface)

git/adapter.go

@@ -74,6 +74,7 @@ type Adapter interface {
 	Merge(ctx context.Context, pr *types.PullRequest, mergeMethod enum.MergeMethod, baseBranch, trackingBranch string,
 		tmpBasePath string, mergeMsg string, identity *types.Identity, env ...string) (types.MergeResult, error)
 	GetMergeBase(ctx context.Context, repoPath, remote, base, head string) (string, string, error)
+	IsAncestor(ctx context.Context, repoPath, ancestorCommitSHA, descendantCommitSHA string) (bool, error)
 	Blame(ctx context.Context, repoPath, rev, file string, lineFrom, lineTo int) types.BlameReader
 	Sync(ctx context.Context, repoPath string, source string, refSpecs []string) error
 

git/adapter/merge.go

@@ -585,6 +585,28 @@ func (a Adapter) GetMergeBase(
 	return strings.TrimSpace(stdout), base, nil
 }
 
+// IsAncestor returns if the provided commit SHA is ancestor of the other commit SHA.
+func (a Adapter) IsAncestor(
+	ctx context.Context,
+	repoPath string,
+	ancestorCommitSHA, descendantCommitSHA string,
+) (bool, error) {
+	if repoPath == "" {
+		return false, ErrRepositoryPathEmpty
+	}
+
+	_, stderr, runErr := git.NewCommand(ctx, "merge-base", "--is-ancestor", ancestorCommitSHA, descendantCommitSHA).
+		RunStdString(&git.RunOpts{Dir: repoPath})
+	if runErr != nil {
+		if runErr.IsExitCode(1) && stderr == "" {
+			return false, nil
+		}
+		return false, processGiteaErrorf(runErr, "failed to check commit ancestry: %v", stderr)
+	}
+
+	return true, nil
+}
+
 // giteaRunStdError is an implementation of the RunStdError interface in the gitea codebase.
 // It allows us to process gitea errors even when using cmd.Run() instead of cmd.RunStdString() or run.StdBytes().
 type giteaRunStdError struct {

git/interface.go

@@ -53,6 +53,7 @@ type Interface interface {
 	GetCommitDivergences(ctx context.Context, params *GetCommitDivergencesParams) (*GetCommitDivergencesOutput, error)
 	CommitFiles(ctx context.Context, params *CommitFilesParams) (CommitFilesResponse, error)
 	MergeBase(ctx context.Context, params MergeBaseParams) (MergeBaseOutput, error)
+	IsAncestor(ctx context.Context, params IsAncestorParams) (IsAncestorOutput, error)
 
 	/*
 	 * Git Cli Service

git/merge.go

@@ -411,3 +411,29 @@ func (s *Service) MergeBase(
 		MergeBaseSHA: result,
 	}, nil
 }
+
+type IsAncestorParams struct {
+	ReadParams
+	AncestorCommitSHA   string
+	DescendantCommitSHA string
+}
+
+type IsAncestorOutput struct {
+	Ancestor bool
+}
+
+func (s *Service) IsAncestor(
+	ctx context.Context,
+	params IsAncestorParams,
+) (IsAncestorOutput, error) {
+	repoPath := getFullPathForRepo(s.reposRoot, params.RepoUID)
+
+	result, err := s.adapter.IsAncestor(ctx, repoPath, params.AncestorCommitSHA, params.DescendantCommitSHA)
+	if err != nil {
+		return IsAncestorOutput{}, err
+	}
+
+	return IsAncestorOutput{
+		Ancestor: result,
+	}, nil
+}