improve handling of GetAllContentsByRef where root path is requested (#2105)

* add failing test for handling / as the path

* workaround issue by passing in what the API expects

Octokit.Tests.Integration/Clients/RepositoryContentsClientTests.cs

@@ -222,6 +222,18 @@ namespace Octokit.Tests.Integration.Clients
                 Assert.Equal(ContentType.Dir, contents.First().Type);
             }
 
+            [IntegrationTest]
+            public async Task GetsContentNonMasterWithRootPath()
+            {
+                var github = Helper.GetAuthenticatedClient();
+
+                var contents = await github
+                    .Repository
+                    .Content
+                    .GetAllContentsByRef("octocat", "Spoon-Knife", "/", reference: "test-branch");
+                Assert.Equal(4, contents.Count);
+            }
+
             [IntegrationTest]
             public async Task GetsDirectoryContentWithRepositoryId()
             {

Octokit/Clients/RepositoryContentsClient.cs

@@ -107,7 +107,9 @@ namespace Octokit
             Ensure.ArgumentNotNullOrEmptyString(path, nameof(path));
             Ensure.ArgumentNotNullOrEmptyString(reference, nameof(reference));
 
-            var url = ApiUrls.RepositoryContent(owner, name, path, reference);
+            var url = (path == "/")
+                ? ApiUrls.RepositoryContent(owner, name, "", reference)
+                : ApiUrls.RepositoryContent(owner, name, path, reference);
 
             return ApiConnection.GetAll<RepositoryContent>(url);
         }