Read and write submodule branch Option #1301

LibGit2Sharp.Tests/SubmoduleFixture.cs

@@ -202,6 +202,26 @@ public void CanInitSubmodule()
             }
         }
 
+        [Fact]
+        public void CanChangeSubmoduleBranch()
+        {
+            var path = SandboxSubmoduleSmallTestRepo();
+            string submoduleName = "submodule_target_wd";
+            string expectedSubmoduleBranch = @"master";
+
+            using (var repo = new Repository(path))
+            {
+                var submodule = repo.Submodules[submoduleName];
+
+                Assert.Null(submodule.Branch);
+
+                submodule.Branch = expectedSubmoduleBranch;
+
+                Assert.NotNull(submodule.Branch);
+                Assert.Equal(submodule.Branch, expectedSubmoduleBranch);
+            }
+        }
+
         [Fact]
         public void UpdatingUninitializedSubmoduleThrows()
         {

LibGit2Sharp/Core/NativeMethods.cs

@@ -1852,6 +1852,17 @@ internal static extern unsafe string git_submodule_path(
         internal static extern unsafe string git_submodule_url(
             git_submodule* submodule);
 
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        [return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(LaxUtf8NoCleanupMarshaler))]
+        internal static extern unsafe string git_submodule_branch(
+            git_submodule* submodule);
+
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern unsafe int git_submodule_set_branch(
+            git_repository* repo,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string name,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string branch);
+
         [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
         internal static extern unsafe git_oid* git_submodule_index_id(
             git_submodule* submodule);

LibGit2Sharp/Core/Proxy.cs

@@ -3020,6 +3020,17 @@ public static unsafe string git_submodule_url(SubmoduleHandle submodule)
             return NativeMethods.git_submodule_url(submodule);
         }
 
+        public static unsafe string git_submodule_branch(SubmoduleHandle submodule)
+        {
+            return NativeMethods.git_submodule_branch(submodule);
+        }
+
+        public static unsafe void git_submodule_set_branch(RepositoryHandle repo, string name, string branch)
+        {
+            var res = NativeMethods.git_submodule_set_branch(repo, name, branch);
+            Ensure.ZeroResult(res);
+        }
+
         public static unsafe ObjectId git_submodule_index_id(SubmoduleHandle submodule)
         {
             return ObjectId.BuildFromPtr(NativeMethods.git_submodule_index_id(submodule));

LibGit2Sharp/Submodule.cs

@@ -18,6 +18,7 @@ public class Submodule : IEquatable<Submodule>, IBelongToARepository
         private readonly string name;
         private readonly string path;
         private readonly string url;
+        private string branch;
         private readonly ILazy<ObjectId> headCommitId;
         private readonly ILazy<ObjectId> indexCommitId;
         private readonly ILazy<ObjectId> workdirCommitId;
@@ -31,12 +32,13 @@ public class Submodule : IEquatable<Submodule>, IBelongToARepository
         protected Submodule()
         { }
 
-        internal Submodule(Repository repo, string name, string path, string url)
+        internal Submodule(Repository repo, string name, string path, string url, string branch)
         {
             this.repo = repo;
             this.name = name;
             this.path = path;
             this.url = url;
+            this.branch = branch;
 
             var commitIds = new SubmoduleLazyGroup(repo, name);
             headCommitId = commitIds.AddLazy(Proxy.git_submodule_head_id);
@@ -64,6 +66,11 @@ internal Submodule(Repository repo, string name, string path, string url)
         /// </summary>
         public virtual string Url { get { return url; } }
 
+        /// <summary>
+        /// The name of the remote branch
+        /// </summary>
+        public virtual string Branch { get { return branch; } set { SetRemoteBranch(value); } }
+
         /// <summary>
         /// The commit ID for this submodule in the current HEAD tree.
         /// </summary>
@@ -152,6 +159,23 @@ private string DebuggerDisplay
             }
         }
 
+        private void SetRemoteBranch(string branch)
+        {
+            using (var handle = Proxy.git_submodule_lookup(repo.Handle, name))
+            {
+                if (handle == null)
+                {
+                    throw new NotFoundException("Submodule lookup failed for '{0}'.",
+                                                name);
+                }
+
+                Proxy.git_submodule_set_branch(repo.Handle, name, branch);
+                Proxy.git_submodule_reload(handle);
+                this.branch = Proxy.git_submodule_branch(handle);
+            }
+
+        }
+
         IRepository IBelongToARepository.Repository { get { return repo; } }
     }
 }

LibGit2Sharp/SubmoduleCollection.cs

@@ -43,7 +43,8 @@ public virtual Submodule this[string name]
 
                 return Lookup(name, handle => new Submodule(repo, name,
                                                             Proxy.git_submodule_path(handle),
-                                                            Proxy.git_submodule_url(handle)));
+                                                            Proxy.git_submodule_url(handle),
+                                                            Proxy.git_submodule_branch(handle)));
             }
         }