Add methods to create a signed commit

First you need to create a buffer which you can apply the signature function to. You can then create the commit object the data and its signature.
libgit2 · ethomson · Apr 27, 2016 · Apr 15, 2016 · Apr 15, 2016 · Apr 15, 2016
commit 508807fbe6767e5d005e01df7ae0dbd235a4a48b
diff --git a/LibGit2Sharp.Tests/CommitFixture.cs b/LibGit2Sharp.Tests/CommitFixture.cs
@@ -1057,10 +1057,7 @@ public void CanPrettifyAMessage()
             Assert.Equal(expected, Commit.PrettifyMessage(input.Replace('#', ';'), ';'));
         }
 
-        [Fact]
-        public void CanExtractSignatureFromCommit()
-        {
-            string commitData = @"tree 6b79e22d69bf46e289df0345a14ca059dfc9bdf6
+        private readonly string signedCommit = @"tree 6b79e22d69bf46e289df0345a14ca059dfc9bdf6
 parent 34734e478d6cf50c27c9d69026d93974d052c454
 author Ben Burkert <ben@benburkert.com> 1358451456 -0800
 committer Ben Burkert <ben@benburkert.com> 1358451456 -0800
@@ -1085,7 +1082,7 @@ committer Ben Burkert <ben@benburkert.com> 1358451456 -0800
 a simple commit which works
 ";
 
-            string signatureData = @"-----BEGIN PGP SIGNATURE-----
+        private readonly string signatureData = @"-----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1.4.12 (Darwin)
 
 iQIcBAABAgAGBQJQ+FMIAAoJEH+LfPdZDSs1e3EQAJMjhqjWF+WkGLHju7pTw2al
@@ -1103,19 +1100,23 @@ a simple commit which works
 =ozeK
 -----END PGP SIGNATURE-----";
 
-            string signedData = @"tree 6b79e22d69bf46e289df0345a14ca059dfc9bdf6
+        private readonly string signedData = @"tree 6b79e22d69bf46e289df0345a14ca059dfc9bdf6
 parent 34734e478d6cf50c27c9d69026d93974d052c454
 author Ben Burkert <ben@benburkert.com> 1358451456 -0800
 committer Ben Burkert <ben@benburkert.com> 1358451456 -0800
 
 a simple commit which works
 ";
 
+
+        [Fact]
+        public void CanExtractSignatureFromCommit()
+        {
             string repoPath = InitNewRepository();
             using (var repo = new Repository(repoPath))
             {
                 var odb = repo.ObjectDatabase;
-                var signedId = odb.Write<Commit>(Encoding.UTF8.GetBytes(commitData));
+                var signedId = odb.Write<Commit>(Encoding.UTF8.GetBytes(signedCommit));
 
                 // Look up the commit to make sure we wrote something valid
                 var commit = repo.Lookup<Commit>(signedId);
@@ -1124,6 +1125,48 @@ a simple commit which works
                 var signatureInfo = Commit.ExtractSignature(repo, signedId, "gpgsig");
                 Assert.Equal(signedData, signatureInfo.SignedData);
                 Assert.Equal(signatureData, signatureInfo.Signature);
+
+                signatureInfo = Commit.ExtractSignature(repo, signedId);
+                Assert.Equal(signedData, signatureInfo.SignedData);
+                Assert.Equal(signatureData, signatureInfo.Signature);
+            }
+        }
+
+        [Fact]
+        public void CanCreateACommitString()
+        {
+            string repoPath = SandboxStandardTestRepo();
+            using (var repo = new Repository(repoPath))
+            {
+                var tipCommit = repo.Head.Tip;
+                var recreatedCommit = Commit.CreateBuffer(
+                    tipCommit.Author,
+                    tipCommit.Committer,
+                    tipCommit.Message,
+                    tipCommit.Tree,
+                    tipCommit.Parents,
+                    false, null);
+
+                var recreatedId = repo.ObjectDatabase.Write<Commit>(Encoding.UTF8.GetBytes(recreatedCommit));
+                Assert.Equal(tipCommit.Id, recreatedId);
+            }
+        }
+
+        [Fact]
+        public void CanCreateASignedCommit()
+        {
+            string repoPath = InitNewRepository();
+            using (var repo = new Repository(repoPath))
+            {
+                var odb = repo.ObjectDatabase;
+                var signedId = odb.Write<Commit>(Encoding.UTF8.GetBytes(signedCommit));
+                var signedId2 = odb.CreateCommitWithSignature(signedData, signatureData);
+
+                Assert.Equal(signedId, signedId2);
+
+                var signatureInfo = Commit.ExtractSignature(repo, signedId2);
+                Assert.Equal(signedData, signatureInfo.SignedData);
+                Assert.Equal(signatureData, signatureInfo.Signature);
             }
         }
     }

diff --git a/LibGit2Sharp/Commit.cs b/LibGit2Sharp/Commit.cs
@@ -164,6 +164,42 @@ public static SignatureInfo ExtractSignature(Repository repo, ObjectId id)
             return Proxy.git_commit_extract_signature(repo.Handle, id, null);
         }
 
+        /// <summary>
+        /// Create a commit in-memory
+        /// <para>
+        /// Prettifing the message includes:
+        /// * Removing empty lines from the beginning and end.
+        /// * Removing trailing spaces from every line.
+        /// * Turning multiple consecutive empty lines between paragraphs into just one empty line.
+        /// * Ensuring the commit message ends with a newline.
+        /// * Removing every line starting with the <paramref name="commentChar"/>.
+        /// </para>
+        /// </summary>
+        /// <param name="author">The <see cref="Signature"/> of who made the change.</param>
+        /// <param name="committer">The <see cref="Signature"/> of who added the change to the repository.</param>
+        /// <param name="message">The description of why a change was made to the repository.</param>
+        /// <param name="tree">The <see cref="Tree"/> of the <see cref="Commit"/> to be created.</param>
+        /// <param name="parents">The parents of the <see cref="Commit"/> to be created.</param>
+        /// <param name="prettifyMessage">True to prettify the message, or false to leave it as is.</param>
+        /// <param name="commentChar">When non null, lines starting with this character will be stripped if prettifyMessage is true.</param>
+        /// <returns>The contents of the commit object.</returns>
+        public static string CreateBuffer(Signature author, Signature committer, string message, Tree tree, IEnumerable<Commit> parents, bool prettifyMessage, char? commentChar)
+        {
+            Ensure.ArgumentNotNull(message, "message");
+            Ensure.ArgumentDoesNotContainZeroByte(message, "message");
+            Ensure.ArgumentNotNull(author, "author");
+            Ensure.ArgumentNotNull(committer, "committer");
+            Ensure.ArgumentNotNull(tree, "tree");
+            Ensure.ArgumentNotNull(parents, "parents");
+
+            if (prettifyMessage)
+            {
+                message = Proxy.git_message_prettify(message, commentChar);
+            }
+
+            return Proxy.git_commit_create_buffer(tree.repo.Handle, author, committer, message, tree, parents.ToArray());
+        }
+
         private class ParentsCollection : ICollection<Commit>
         {
             private readonly Lazy<ICollection<Commit>> _parents;

diff --git a/LibGit2Sharp/Core/NativeMethods.cs b/LibGit2Sharp/Core/NativeMethods.cs
@@ -316,6 +316,27 @@ internal static extern unsafe int git_commit_create_from_ids(
             UIntPtr parentCount,
             [MarshalAs(UnmanagedType.LPArray)] [In] IntPtr[] parents);
 
+        [DllImport(libgit2)]
+        internal static extern unsafe int git_commit_create_buffer(
+            GitBuf res,
+            git_repository* repo,
+            git_signature* author,
+            git_signature* committer,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string encoding,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string message,
+            git_object* tree,
+            UIntPtr parent_count,
+            IntPtr* parents /* git_commit** originally */);
+
+        [DllImport(libgit2)]
+        internal static extern unsafe int git_commit_create_with_signature(
+            out GitOid id,
+            git_repository* repo,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string commit_content,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string signature,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string signature_field);
+
+
         [DllImport(libgit2)]
         [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(LaxUtf8NoCleanupMarshaler))]
         internal static extern unsafe string git_commit_message(git_object* commit);

diff --git a/LibGit2Sharp/Core/Proxy.cs b/LibGit2Sharp/Core/Proxy.cs
@@ -388,6 +388,61 @@ public static unsafe ObjectId git_commit_create(
             }
         }
 
+        public static unsafe string git_commit_create_buffer(
+            RepositoryHandle repo,
+            Signature author,
+            Signature committer,
+            string message,
+            Tree tree,
+            Commit[] parents)
+        {
+            using (SignatureHandle authorHandle = author.BuildHandle())
+            using (SignatureHandle committerHandle = committer.BuildHandle())
+            using (var treeHandle = Proxy.git_object_lookup(tree.repo.Handle, tree.Id, GitObjectType.Tree))
+            using (var buf = new GitBuf())
+            {
+                ObjectHandle[] handles = new ObjectHandle[0];
+                try
+                {
+                    handles = parents.Select(c => Proxy.git_object_lookup(c.repo.Handle, c.Id, GitObjectType.Commit)).ToArray();
+                    var ptrs = handles.Select(p => p.AsIntPtr()).ToArray();
+                    int res;
+                    fixed(IntPtr* objs = ptrs)
+                    {
+                        res = NativeMethods.git_commit_create_buffer(buf,
+                            repo,
+                            authorHandle,
+                            committerHandle,
+                            null,
+                            message,
+                            treeHandle,
+                            new UIntPtr((ulong)parents.LongCount()),
+                            objs);
+                    }
+                    Ensure.ZeroResult(res);
+                }
+                finally
+                {
+                    foreach (var handle in handles)
+                    {
+                        handle.Dispose();
+                    }
+                }
+
+                return LaxUtf8Marshaler.FromNative(buf.ptr);
+            }
+        }
+
+        public static unsafe ObjectId git_commit_create_with_signature(RepositoryHandle repo, string commitContent,
+            string signature, string field)
+        {
+            GitOid id;
+            int res = NativeMethods.git_commit_create_with_signature(out id, repo, commitContent, signature, field);
+            Ensure.ZeroResult(res);
+
+            return id;
+        }
+
         public static unsafe string git_commit_message(ObjectHandle obj)
         {
             return NativeMethods.git_commit_message(obj);

diff --git a/LibGit2Sharp/GitObject.cs b/LibGit2Sharp/GitObject.cs
@@ -28,7 +28,7 @@ public abstract class GitObject : IEquatable<GitObject>, IBelongToARepository
         /// <summary>
         /// The <see cref="Repository"/> containing the object.
         /// </summary>
-        protected readonly Repository repo;
+        internal readonly Repository repo;
 
         /// <summary>
         /// Needed for mocking purposes.

diff --git a/LibGit2Sharp/ObjectDatabase.cs b/LibGit2Sharp/ObjectDatabase.cs
@@ -422,6 +422,32 @@ public virtual Commit CreateCommit(Signature author, Signature committer, string
             return commit;
         }
 
+        /// <summary>
+        /// Inserts a <see cref="Commit"/> into the object database after attaching the given signature.
+        /// </summary>
+        /// <param name="commitContent">The raw unsigned commit</param>
+        /// <param name="signature">The signature data </param>
+        /// <param name="field">The header field in the commit in which to store the signature</param>
+        /// <returns>The created <see cref="Commit"/>.</returns>
+        public virtual ObjectId CreateCommitWithSignature(string commitContent, string signature, string field)
+        {
+            return Proxy.git_commit_create_with_signature(repo.Handle, commitContent, signature, field);
+        }
+
+        /// <summary>
+        /// Inserts a <see cref="Commit"/> into the object database after attaching the given signature.
+        /// <para>
+        /// This overload uses the default header field of "gpgsig"
+        /// </para>
+        /// </summary>
+        /// <param name="commitContent">The raw unsigned commit</param>
+        /// <param name="signature">The signature data </param>
+        /// <returns>The created <see cref="Commit"/>.</returns>
+        public virtual ObjectId CreateCommitWithSignature(string commitContent, string signature)
+        {
+            return Proxy.git_commit_create_with_signature(repo.Handle, commitContent, signature, null);
+        }
+
         /// <summary>
         /// Inserts a <see cref="TagAnnotation"/> into the object database, pointing to a specific <see cref="GitObject"/>.
         /// </summary>