1 files changed, 136 insertions, 0 deletions
diff --git a/cmd/gitaly-git2go/submodule.go b/cmd/gitaly-git2go/submodule.go
new file mode 100644
index 000000000..d256188b1
--- /dev/null
+++ b/cmd/gitaly-git2go/submodule.go
@@ -0,0 +1,136 @@
+// +build static,system_libgit2
+
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"time"
+
+	git "github.com/libgit2/git2go/v30"
+	"gitlab.com/gitlab-org/gitaly/internal/git2go"
+)
+
+type submoduleSubcommand struct {
+	request string
+}
+
+func (cmd *submoduleSubcommand) Flags() *flag.FlagSet {
+	flags := flag.NewFlagSet("submodule", flag.ExitOnError)
+	flags.StringVar(&cmd.request, "request", "", "git2go.SubmoduleCommand")
+	return flags
+}
+
+func (cmd *submoduleSubcommand) Run(_ context.Context, _ io.Reader, w io.Writer) error {
+	request, err := git2go.SubmoduleCommandFromSerialized(cmd.request)
+	if err != nil {
+		return fmt.Errorf("deserializing submodule command request: %w", err)
+	}
+
+	if request.AuthorDate.IsZero() {
+		request.AuthorDate = time.Now()
+	}
+
+	smCommitOID, err := git.NewOid(request.CommitSHA)
+	if err != nil {
+		return fmt.Errorf("converting %s to OID: %w", request.CommitSHA, err)
+	}
+
+	repo, err := git.OpenRepository(request.Repository)
+	if err != nil {
+		return fmt.Errorf("open repository: %w", err)
+	}
+
+	fullBranchRefName := "refs/heads/" + request.Branch
+	o, err := repo.RevparseSingle(fullBranchRefName)
+	if err != nil {
+		return fmt.Errorf("%s: %w", git2go.LegacyErrPrefixInvalidBranch, err) //nolint
+	}
+
+	startCommit, err := o.AsCommit()
+	if err != nil {
+		return fmt.Errorf("peeling %s as a commit: %w", o.Id(), err)
+	}
+
+	rootTree, err := startCommit.Tree()
+	if err != nil {
+		return fmt.Errorf("root tree from starting commit: %w", err)
+	}
+
+	index, err := git.NewIndex()
+	if err != nil {
+		return fmt.Errorf("creating new index: %w", err)
+	}
+
+	if err := index.ReadTree(rootTree); err != nil {
+		return fmt.Errorf("reading root tree into index: %w", err)
+	}
+
+	smEntry, err := index.EntryByPath(request.Submodule, 0)
+	if err != nil {
+		return fmt.Errorf(
+			"%s: %w",
+			git2go.LegacyErrPrefixInvalidSubmodulePath, err,
+		) //nolint
+	}
+
+	if smEntry.Id.Cmp(smCommitOID) == 0 {
+		//nolint
+		return fmt.Errorf(
+			"The submodule %s is already at %s",
+			request.Submodule, request.CommitSHA,
+		)
+	}
+
+	if smEntry.Mode != git.FilemodeCommit {
+		return fmt.Errorf(
+			"%s: %w",
+			git2go.LegacyErrPrefixInvalidSubmodulePath, err,
+		) //nolint
+	}
+
+	newEntry := *smEntry      // copy by value
+	newEntry.Id = smCommitOID // assign new commit SHA
+	if err := index.Add(&newEntry); err != nil {
+		return fmt.Errorf("add new submodule entry to index: %w", err)
+	}
+
+	newRootTreeOID, err := index.WriteTreeTo(repo)
+	if err != nil {
+		return fmt.Errorf("write index to repo: %w", err)
+	}
+
+	newTree, err := repo.LookupTree(newRootTreeOID)
+	if err != nil {
+		return fmt.Errorf("looking up new submodule entry root tree: %w", err)
+	}
+
+	committer := git.Signature(
+		git2go.NewSignature(
+			request.AuthorName,
+			request.AuthorMail,
+			request.AuthorDate,
+		),
+	)
+	newCommitOID, err := repo.CreateCommit(
+		"", // caller should update branch with hooks
+		&committer,
+		&committer,
+		request.Message,
+		newTree,
+		startCommit,
+	)
+	if err != nil {
+		// nolint
+		return fmt.Errorf(
+			"%s: %w",
+			git2go.LegacyErrPrefixFailedCommit, err,
+		)
+	}
+
+	return git2go.SubmoduleResult{
+		CommitID: newCommitOID.String(),
+	}.SerializeTo(w)
+}