Add repo trees (#94)

* add repo trees

* Update copyright

gitea/repo_tree.go

@@ -0,0 +1,35 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package gitea
+
+import (
+	"fmt"
+)
+
+// GitEntry represents a git tree
+type GitEntry struct {
+	Path string `json:"path"`
+	Mode string `json:"mode"`
+	Type string `json:"type"`
+	Size int64  `json:"size"`
+	SHA  string `json:"sha"`
+	URL  string `json:"url"`
+}
+
+// GitTreeResponse returns a git tree
+type GitTreeResponse struct {
+	SHA       string     `json:"sha"`
+	URL       string     `json:"url"`
+	Entries   []GitEntry `json:"tree"`
+	Truncated bool       `json:"truncated"`
+}
+
+// GetTrees downloads a file of repository, ref can be branch/tag/commit.
+// e.g.: ref -> master, tree -> macaron.go(no leading slash)
+func (c *Client) GetTrees(user, repo, ref string) (*GitTreeResponse, error) {
+	var trees GitTreeResponse
+	_, err := c.getResponse("GET", fmt.Sprintf("/repos/%s/%s/git/trees/%s", user, repo, ref), nil, nil)
+	return &trees, err
+}