Add new fields to NewRepository request and update RepositoriesClient.Create() method to specify preview accepts header and fix impacted unit tests

Add integration test for Create Repository with merge method specified

Octokit.Tests.Integration/Clients/RepositoriesClientTests.cs

@@ -268,6 +268,36 @@ public class RepositoriesClientTests
                 Task.WhenAll(deleteRepos).Wait();
             }
         }
+
+        [IntegrationTest]
+        public async Task CreatesARepositoryWithRequestedMergeMethod()
+        {
+            var github = Helper.GetAuthenticatedClient();
+            var repoName = Helper.MakeNameWithTimestamp("public-repo");
+
+            var newRepository = new NewRepository(repoName)
+            {
+                AllowMergeCommit = false,
+                AllowSquashMerge = true,
+                AllowRebaseMerge = false
+            };
+
+            using (var context = await github.CreateRepositoryContext(newRepository))
+            {
+                var createdRepository = context.Repository;
+
+                Assert.Equal(repoName, createdRepository.Name);
+                Assert.False(createdRepository.AllowMergeCommit);
+                Assert.True(createdRepository.AllowSquashMerge);
+                Assert.False(createdRepository.AllowRebaseMerge);
+
+                var repository = await github.Repository.Get(Helper.UserName, repoName);
+                Assert.Equal(repoName, repository.Name);
+                Assert.False(repository.AllowMergeCommit);
+                Assert.True(repository.AllowSquashMerge);
+                Assert.False(repository.AllowRebaseMerge);
+            }
+        }
     }
 
     public class TheCreateMethodForOrganization