repository: Resolve commit when cloning annotated tag, fixes src-d#557

Author: orirawlings

repository.go

@@ -400,6 +400,25 @@ func (r *Repository) DeleteRemote(name string) error {
 	return r.Storer.SetConfig(cfg)
 }
 
+func (r *Repository) resolveToCommitHash(h plumbing.Hash) (plumbing.Hash, error) {
+	obj, err := r.Storer.EncodedObject(plumbing.AnyObject, h)
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+	switch obj.Type() {
+	case plumbing.TagObject:
+		t, err := object.DecodeTag(r.Storer, obj)
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+		return r.resolveToCommitHash(t.Target)
+	case plumbing.CommitObject:
+		return h, nil
+	default:
+		return plumbing.ZeroHash, errors.New("Unable to resolve to commit")
+	}
+}
+
 // Clone clones a remote repository
 func (r *Repository) clone(ctx context.Context, o *CloneOptions) error {
 	if err := o.Validate(); err != nil {
@@ -431,7 +450,11 @@ func (r *Repository) clone(ctx context.Context, o *CloneOptions) error {
 			return err
 		}
 
-		if err := w.Reset(&ResetOptions{Commit: head.Hash()}); err != nil {
+		h, err := r.resolveToCommitHash(head.Hash())
+		if err != nil {
+			return err
+		}
+		if err := w.Reset(&ResetOptions{Commit: h}); err != nil {
 			return err
 		}
 

repository_test.go

@@ -651,6 +651,27 @@ func (s *RepositorySuite) TestCloneDetachedHEADAndShallow(c *C) {
 	c.Assert(count, Equals, 15)
 }
 
+func (s *RepositorySuite) TestCloneDetachedHEADAnnotatedTag(c *C) {
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{
+		URL:           s.GetLocalRepositoryURL(fixtures.ByTag("tags").One()),
+		ReferenceName: plumbing.ReferenceName("refs/tags/annotated-tag"),
+	})
+	c.Assert(err, IsNil)
+
+	head, err := r.Reference(plumbing.HEAD, false)
+	c.Assert(err, IsNil)
+	c.Assert(head, NotNil)
+	c.Assert(head.Type(), Equals, plumbing.HashReference)
+	c.Assert(head.Hash().String(), Equals, "f7b877701fbf855b44c0a9e86f3fdce2c298b07f")
+
+	count := 0
+	objects, err := r.Objects()
+	c.Assert(err, IsNil)
+	objects.ForEach(func(object.Object) error { count++; return nil })
+	c.Assert(count, Equals, 7)
+}
+
 func (s *RepositorySuite) TestPush(c *C) {
 	url := c.MkDir()
 	server, err := PlainInit(url, true)