Put optimization behind temporary feature flag

gitindex/index.go

@@ -408,11 +408,23 @@ func indexGitRepo(opts Options, config gitIndexConfig) (bool, error) {
 
 	opts.BuildOptions.RepositoryDescription.Source = opts.RepoDir
 
-	repo, repoCloser, err := openRepo(opts.RepoDir)
-	if err != nil {
-		return false, fmt.Errorf("openRepo: %w", err)
+	var repo *git.Repository
+
+	// TODO: remove this feature flag once we test this on a large-scale instance.
+	optimizeRepoOpen := os.Getenv("ZOEKT_ENABLE_GOGIT_OPTIMIZATION")
+	if b, err := strconv.ParseBool(optimizeRepoOpen); b && err == nil {
+		var repoCloser io.Closer
+		repo, repoCloser, err = openRepo(opts.RepoDir)
+		if err != nil {
+			return false, fmt.Errorf("openRepo: %w", err)
+		}
+		defer repoCloser.Close()
+	} else {
+		repo, err = git.PlainOpen(opts.RepoDir)
+		if err != nil {
+			return false, fmt.Errorf("git.PlainOpen: %w", err)
+		}
 	}
-	defer repoCloser.Close()
 
 	if err := setTemplatesFromConfig(&opts.BuildOptions.RepositoryDescription, opts.RepoDir); err != nil {
 		log.Printf("setTemplatesFromConfig(%s): %s", opts.RepoDir, err)