Don't force default branch in deps ingest and fix segfaults (#5143)

This allows us to auto-discover a default branch if the user does not
set it. The previous setup was forcing that we'd always use the
"default" branch, thus bypassing autodiscovery.

It also had segfaults in the case where the repo configuration was not
set.

Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>

internal/engine/ingester/deps/deps.go

@@ -83,9 +83,9 @@ func (gi *Deps) Ingest(ctx context.Context, ent protoreflect.ProtoMessage, param
 
 func (gi *Deps) ingestRepository(ctx context.Context, repo *pb.Repository, params map[string]any) (*interfaces.Result, error) {
 	var logger = zerolog.Ctx(ctx)
-	userCfg := &Config{
-		Branch: defaultBranch,
-	}
+	// the branch is left unset since we want to auto-discover it
+	// in case it's not explicitly set
+	userCfg := &Config{}
 	if err := mapstructure.Decode(params, userCfg); err != nil {
 		return nil, fmt.Errorf("failed to read dependency ingester configuration from params: %w", err)
 	}
@@ -143,16 +143,16 @@ func (gi *Deps) ingestRepository(ctx context.Context, repo *pb.Repository, param
 	}, nil
 }
 
-func (gi *Deps) getBranch(repo *pb.Repository, branch string) string {
+func (gi *Deps) getBranch(repo *pb.Repository, userConfigBranch string) string {
 	// If the user has specified a branch, use that
-	if branch != "" {
-		return branch
+	if userConfigBranch != "" {
+		return userConfigBranch
 	}
 
 	// If the branch is provided in the rule-type
 	// configuration, use that
-	if gi.cfg.GetRepo().Branch != "" {
-		return gi.cfg.GetRepo().Branch
+	if gi.cfg.GetRepo().GetBranch() != "" {
+		return gi.cfg.GetRepo().GetBranch()
 	}
 	if repo.GetDefaultBranch() != "" {
 		return repo.GetDefaultBranch()