Add a general Write<T> method to ObjectDatabase

We have some methods for creating objects from specific data, but not
for creating it out of an existing buffer.

Author: carlosmn

LibGit2Sharp/Core/NativeMethods.cs

@@ -919,6 +919,9 @@ internal static extern unsafe int git_odb_foreach(
         [DllImport(libgit2)]
         internal static extern unsafe void git_odb_stream_free(git_odb_stream* stream);
 
+        [DllImport(libgit2)]
+        internal static extern unsafe int git_odb_write(out GitOid id, git_odb *odb, byte* data, UIntPtr len, GitObjectType type);
+
         [DllImport(libgit2)]
         internal static extern unsafe git_oid* git_object_id(git_object* obj);
 

LibGit2Sharp/Core/Proxy.cs

@@ -1510,6 +1510,19 @@ public static unsafe ObjectId git_odb_stream_finalize_write(OdbStreamHandle stre
             return id;
         }
 
+        public static unsafe ObjectId git_odb_write(ObjectDatabaseHandle odb, byte[] data, ObjectType type)
+        {
+            GitOid id;
+            int res;
+            fixed(byte* p = data)
+            {
+                res = NativeMethods.git_odb_write(out id, odb, p, new UIntPtr((ulong)data.LongLength), type.ToGitObjectType());
+            }
+            Ensure.ZeroResult(res);
+
+            return id;
+        }
+
         #endregion
 
         #region git_patch_

LibGit2Sharp/ObjectDatabase.cs

@@ -177,6 +177,16 @@ public int Provider(IntPtr content, int max_length, IntPtr data)
             }
         }
 
+        /// <summary>
+        /// Write an object to the object database
+        /// </summary>
+        /// <param name="data">The contents of the object</param>
+        /// <typeparam name="T">The type of object to write</typeparam>
+        public virtual ObjectId Write<T>(byte[] data) where T : GitObject
+        {
+            return Proxy.git_odb_write(handle, data, GitObject.TypeToKindMap[typeof(T)]);
+        }
+
         /// <summary>
         /// Inserts a <see cref="Blob"/> into the object database, created from the content of a stream.
         /// <para>Optionally, git filters will be applied to the content before storing it.</para>