Add GIT_EUSER to OdbBackend exposed return codes

Author: nulltoken

LibGit2Sharp.Tests/OdbBackendFixture.cs

@@ -311,9 +311,14 @@ public override int ReadStream(ObjectId oid, out OdbBackendStream stream)
 
             public override int ForEach(ForEachCallback callback)
             {
-                foreach (var mockGitObject in m_objectIdToContent)
+                foreach (var objectId in m_objectIdToContent.Keys)
                 {
-                    callback(mockGitObject.Key);
+                    int result = callback(objectId);
+
+                    if (result != (int)ReturnCode.GIT_OK)
+                    {
+                        return result;
+                    }
                 }
 
                 return (int)ReturnCode.GIT_OK;

LibGit2Sharp/OdbBackend.cs

@@ -650,6 +650,11 @@ protected enum ReturnCode
             /// The given short oid is ambiguous.
             /// </summary>
             GIT_EAMBIGUOUS = -5,
+
+            /// <summary>
+            /// Interruption of the foreach() callback is requested.
+            /// </summary>
+            GIT_EUSER = -7,
         }
     }
 }