Add support for git push with custom headers

Author: evolvedlight

LibGit2Sharp/Network.cs

@@ -376,6 +376,7 @@ public virtual void Push(Remote remote, IEnumerable<string> pushRefSpecs, PushOp
                                           PackbuilderDegreeOfParallelism = pushOptions.PackbuilderDegreeOfParallelism,
                                           RemoteCallbacks = gitCallbacks,
                                           ProxyOptions = new GitProxyOptions { Version = 1 },
+                                          CustomHeaders = pushOptions.CustomHeaders?.Length > 0 ? GitStrArrayManaged.BuildFrom(pushOptions.CustomHeaders) : new GitStrArrayManaged()
                                       });
             }
         }

LibGit2Sharp/PushOptions.cs

@@ -27,6 +27,27 @@ public sealed class PushOptions
         /// </summary>
         public int PackbuilderDegreeOfParallelism { get; set; }
 
+        /// <summary>
+        /// Get/Set the custom headers.
+        /// 
+        /// <para> 
+        /// This allows you to set custom headers (e.g. X-Forwarded-For, 
+        /// X-Request-Id, etc),
+        /// </para>
+        /// </summary>
+        /// <remarks>
+        /// Libgit2 sets some headers for HTTP requests (User-Agent, Host, 
+        /// Accept, Content-Type, Transfer-Encoding, Content-Length, Accept) that
+        /// cannot be overriden.
+        /// </remarks>
+        /// <example>
+        /// var fetchOptions - new FetchOptions() {
+        ///     CustomHeaders = new String[] {"X-Request-Id: 12345"}
+        /// };
+        /// </example>
+        /// <value>The custom headers string array</value>
+        public string[] CustomHeaders { get; set; } 
+
         /// <summary>
         /// Delegate to report errors when updating references on the remote.
         /// </summary>