Leading slash in ListMergeRequestDiffs API causes 404

[Alfred Yip]

go-gitlab/merge_requests.go

Line 513 in 7d2bd21

 u := fmt.Sprintf("/projects/%s/merge_requests/%d/diffs", PathEscape(project), mergeRequest) 

GET https://gitlab.example.com/api/v4//projects/123/merge_requests/123/diffs: 404 {error: 404 Not Found}

[Sander van Harmelen]

Fixed by #1808