Added missing GetSingleTag method to TagService (#93)

tags.go

@@ -68,6 +68,32 @@ func (s *TagsService) ListTags(pid interface{}) ([]*Tag, *Response, error) {
 	return t, resp, err
 }
 
+// Get a specific repository tag determined by its name. It returns 200 together
+// with the tag information if the tag exists. It returns 404 if the tag does not exist.
+//
+// GitLab API docs:
+// https://docs.gitlab.com/ce/api/tags.html#get-a-single-repository-tag
+func (s *TagsService) GetSingleTag(pid interface{}, tag string) (*Tag, *Response, error) {
+	project, err := parseID(pid)
+	if err != nil {
+		return nil, nil, err
+	}
+	u := fmt.Sprintf("projects/%s/repository/tags/%s", url.QueryEscape(project), tag)
+
+	req, err := s.client.NewRequest("GET", u, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var t *Tag
+	resp, err := s.client.Do(req, &t)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return t, resp, err
+}
+
 // CreateTagOptions represents the available CreateTag() options.
 //
 // GitLab API docs: