added overloads with repoId

Octokit.Reactive/Clients/IObservableMergingClient.cs

@@ -2,6 +2,12 @@
 
 namespace Octokit.Reactive
 {
+    /// <summary>
+    /// A client for GitHub's Git Merging API.
+    /// </summary>
+    /// <remarks>
+    /// See the <a href="https://developer.github.com/v3/repos/merging/">Git Merging API documentation</a> for more information.
+    /// </remarks>
     public interface IObservableMergingClient
     {
         /// <summary>
@@ -15,5 +21,16 @@ namespace Octokit.Reactive
         /// <param name="merge">The merge to create</param>
         /// <returns></returns>
         IObservable<Merge> Create(string owner, string name, NewMerge merge);
+
+        /// <summary>
+        /// Create a merge for a given repository
+        /// </summary>
+        /// <remarks>
+        /// http://developer.github.com/v3/repos/merging/#perform-a-merge
+        /// </remarks>
+        /// <param name="repositoryId">The ID of the repository</param>
+        /// <param name="merge">The merge to create</param>
+        /// <returns></returns>
+        IObservable<Merge> Create(int repositoryId, NewMerge merge);
     }
 }