Implemented FindTag for github driver.

scm/driver/github/git.go

@@ -31,7 +31,10 @@ func (s *gitService) FindCommit(ctx context.Context, repo, ref string) (*scm.Com
 }
 
 func (s *gitService) FindTag(ctx context.Context, repo, name string) (*scm.Reference, *scm.Response, error) {
-	return nil, nil, scm.ErrNotSupported
+	path := fmt.Sprintf("repos/%s/git/ref/tags/%s", repo, name)
+	out := new(ref)
+	res, err := s.client.do(ctx, "GET", path, nil, out)
+	return convertRef(out), res, err
 }
 
 func (s *gitService) ListBranches(ctx context.Context, repo string, opts scm.ListOptions) ([]*scm.Reference, *scm.Response, error) {
@@ -102,6 +105,14 @@ type commit struct {
 	Files []*file `json:"files"`
 }
 
+type ref struct {
+	Ref    string `json:"ref"`
+	Object struct {
+		Type string `json:"type"`
+		Sha  string `json:"sha"`
+	} `json:"object"`
+}
+
 type compare struct {
 	Files []*file `json:"files"`
 }
@@ -152,6 +163,14 @@ func convertBranch(from *branch) *scm.Reference {
 	}
 }
 
+func convertRef(from *ref) *scm.Reference {
+	return &scm.Reference{
+		Name: scm.TrimRef(from.Ref),
+		Path: from.Ref,
+		Sha:  from.Object.Sha,
+	}
+}
+
 func convertTagList(from []*branch) []*scm.Reference {
 	to := []*scm.Reference{}
 	for _, v := range from {

scm/driver/github/git_test.go

@@ -77,11 +77,33 @@ func TestGitFindBranch(t *testing.T) {
 }
 
 func TestGitFindTag(t *testing.T) {
-	git := new(gitService)
-	_, _, err := git.FindTag(context.Background(), "octocat/hello-world", "v1.0")
-	if err != scm.ErrNotSupported {
-		t.Errorf("Expect Not Supported error")
+	defer gock.Off()
+
+	gock.New("https://api.github.com").
+		Get("/repos/octocat/hello-world/git/ref/tags/v0.1").
+		Reply(200).
+		Type("application/json").
+		SetHeaders(mockHeaders).
+		File("testdata/tag.json")
+
+	client := NewDefault()
+	got, res, err := client.Git.FindTag(context.Background(), "octocat/hello-world", "v0.1")
+	if err != nil {
+		t.Error(err)
+		return
 	}
+
+	want := new(scm.Reference)
+	raw, _ := ioutil.ReadFile("testdata/tag.json.golden")
+	json.Unmarshal(raw, &want)
+
+	if diff := cmp.Diff(got, want); diff != "" {
+		t.Errorf("Unexpected Results")
+		t.Log(diff)
+	}
+
+	t.Run("Request", testRequest(res))
+	t.Run("Rate", testRate(res))
 }
 
 func TestGitListCommits(t *testing.T) {

scm/driver/github/testdata/tag.json

@@ -0,0 +1,10 @@
+{
+    "ref": "refs/tags/v0.1",
+    "node_id": "MDY6Q29tbWl0MTI5NjI2OTo3ZmQxYTYwYjAxZjkxYjMxNGY1OTk1NWE0ZTRkNGU4MGQ4ZWRmMTFk",
+    "url": "https://api.github.com/repos/octocat/Hello-World/git/refs/tags/v0.1",
+    "object": {
+        "sha": "7fd1a60b01f91b314f59955a4e4d4e80d8edf11d",
+        "type": "commit",
+        "url": "https://api.github.com/repos/octocat/Hello-World/git/commits/7fd1a60b01f91b314f59955a4e4d4e80d8edf11d"
+    }
+}

scm/driver/github/testdata/tag.json.golden

@@ -0,0 +1,5 @@
+{
+    "Name": "v0.1",
+    "Path": "refs/tags/v0.1",
+    "Sha": "7fd1a60b01f91b314f59955a4e4d4e80d8edf11d"
+}