Fixed cloning of a single tag

Relates to src-d#870

Author: fkorotkov

remote.go

@@ -619,15 +619,15 @@ func getHaves(
 	return result, nil
 }
 
-const refspecTag = "+refs/tags/*:refs/tags/*"
+const refspecAllTags = "+refs/tags/*:refs/tags/*"
 
 func calculateRefs(
 	spec []config.RefSpec,
 	remoteRefs storer.ReferenceStorer,
 	tagMode TagMode,
 ) (memory.ReferenceStorage, error) {
 	if tagMode == AllTags {
-		spec = append(spec, refspecTag)
+		spec = append(spec, refspecAllTags)
 	}
 
 	refs := make(memory.ReferenceStorage)

repository.go

@@ -583,7 +583,7 @@ func (r *Repository) clone(ctx context.Context, o *CloneOptions) error {
 }
 
 const (
-	refspecTagWithDepth     = "+refs/tags/%s:refs/tags/%[1]s"
+	refspecTag              = "+refs/tags/%s:refs/tags/%[1]s"
 	refspecSingleBranch     = "+refs/heads/%s:refs/remotes/%s/%[1]s"
 	refspecSingleBranchHEAD = "+HEAD:refs/remotes/%s/HEAD"
 )
@@ -592,8 +592,8 @@ func (r *Repository) cloneRefSpec(o *CloneOptions, c *config.RemoteConfig) []con
 	var rs string
 
 	switch {
-	case o.ReferenceName.IsTag() && o.Depth > 0:
-		rs = fmt.Sprintf(refspecTagWithDepth, o.ReferenceName.Short())
+	case o.ReferenceName.IsTag():
+		rs = fmt.Sprintf(refspecTag, o.ReferenceName.Short())
 	case o.SingleBranch && o.ReferenceName == plumbing.HEAD:
 		rs = fmt.Sprintf(refspecSingleBranchHEAD, c.Name)
 	case o.SingleBranch:

repository_test.go

@@ -846,7 +846,33 @@ func (s *RepositorySuite) TestCloneDetachedHEAD(c *C) {
 	objects, err := r.Objects()
 	c.Assert(err, IsNil)
 	objects.ForEach(func(object.Object) error { count++; return nil })
-	c.Assert(count, Equals, 31)
+	c.Assert(count, Equals, 28)
+}
+
+func (s *RepositorySuite) TestCloneDetachedHEADAndSingle(c *C) {
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{
+		URL:           s.GetBasicLocalRepositoryURL(),
+		ReferenceName: plumbing.ReferenceName("refs/tags/v1.0.0"),
+		SingleBranch:  true,
+	})
+	c.Assert(err, IsNil)
+
+	cfg, err := r.Config()
+	c.Assert(err, IsNil)
+	c.Assert(cfg.Branches, HasLen, 0)
+
+	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, "6ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	count := 0
+	objects, err := r.Objects()
+	c.Assert(err, IsNil)
+	objects.ForEach(func(object.Object) error { count++; return nil })
+	c.Assert(count, Equals, 28)
 }
 
 func (s *RepositorySuite) TestCloneDetachedHEADAndShallow(c *C) {