Update gitea go-sdk to v0.15.0 (#385)

Update "code.gitea.io/sdk/gitea" to latest release

Reviewed-on: https://gitea.com/gitea/tea/pulls/385
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Co-committed-by: 6543 <6543@obermui.de>

vendor/code.gitea.io/sdk/gitea/repo_tree.go

@@ -31,6 +31,9 @@ type GitTreeResponse struct {
 // 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, recursive bool) (*GitTreeResponse, *Response, error) {
+	if err := escapeValidatePathSegments(&user, &repo, &ref); err != nil {
+		return nil, nil, err
+	}
 	trees := new(GitTreeResponse)
 	var path = fmt.Sprintf("/repos/%s/%s/git/trees/%s", user, repo, ref)
 	if recursive {