Fix submodule nil check (#35096)

Fix  #35095

Author: wxiaoguang

modules/git/commit_info.go

@@ -15,7 +15,7 @@ type CommitInfo struct {
 func getCommitInfoSubmoduleFile(repoLink string, entry *TreeEntry, commit *Commit, treePathDir string) (*CommitSubmoduleFile, error) {
 	fullPath := path.Join(treePathDir, entry.Name())
 	submodule, err := commit.GetSubModule(fullPath)
-	if err != nil {
+	if submodule == nil || err != nil {
 		return nil, err
 	}
 	return NewCommitSubmoduleFile(repoLink, fullPath, submodule.URL, entry.ID.String()), nil

modules/git/commit_info_test.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 const (
@@ -120,6 +121,16 @@ func TestEntries_GetCommitsInfo(t *testing.T) {
 	defer clonedRepo1.Close()
 
 	testGetCommitsInfo(t, clonedRepo1)
+
+	t.Run("NonExistingSubmoduleAsNil", func(t *testing.T) {
+		commit, err := bareRepo1.GetCommit("HEAD")
+		require.NoError(t, err)
+		tree, err := commit.GetTreeEntryByPath("file1.txt")
+		require.NoError(t, err)
+		cisf, err := getCommitInfoSubmoduleFile("/any/repo-link", tree, commit, "")
+		require.NoError(t, err)
+		assert.Nil(t, cisf)
+	})
 }
 
 func BenchmarkEntries_GetCommitsInfo(b *testing.B) {

modules/git/commit_submodule.go

@@ -35,7 +35,8 @@ func (c *Commit) GetSubModules() (*ObjectCache[*SubModule], error) {
 	return c.submoduleCache, nil
 }
 
-// GetSubModule get the submodule according entry name
+// GetSubModule gets the submodule by the entry name.
+// It returns "nil, nil" if the submodule does not exist, caller should always remember to check the "nil"
 func (c *Commit) GetSubModule(entryName string) (*SubModule, error) {
 	modules, err := c.GetSubModules()
 	if err != nil {