Exposed git_merge_base as CommitCollection.GetMergeBase(...)

LibGit2Sharp.Tests/CommitFixture.cs

@@ -37,6 +37,167 @@ public void CanCorrectlyCountCommitsWhenSwitchingToAnotherBranch()
             }
         }
 
+        /* 
+         * BareTestRepoPath structure
+
+            * commit 4c062a6361ae6959e06292c1fa5e2822d9c96345
+            |
+            *   commit be3563ae3f795b2b4353bcce3a527ad0a4f7f644
+            |\ 
+            | |
+            | * commit c47800c7266a2be04c571c04d5a6614691ea99bd
+            | |
+            * | commit 9fd738e8f7967c078dceed8190330fc8648ee56a
+            | |
+            * | commit 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+            |/  
+            |
+            * commit 5b5b025afb0b4c913b4c338a42934a3863bf3644
+            |
+            * commit 8496071c1b46c854b31185ea97743be6a877447
+
+        */
+        [Fact]
+        public void CanCorrectlyFindCommonAncestorForTwoCommits()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("c47800c7266a2be04c571c04d5a6614691ea99bd");
+
+                Commit second = repo.Lookup<Commit>("9fd738e8f7967c078dceed8190330fc8648ee56a");
+
+                Commit ancestor = repo.Commits.FindCommonAncestor(first, second);
+
+                Assert.NotNull(ancestor);
+
+                ancestor.Id.Sha.ShouldEqual("5b5b025afb0b4c913b4c338a42934a3863bf3644");
+            }
+        }
+
+        [Fact]
+        public void CanCorrectlyFindCommonAncestorForTwoCommitsAsEnumerable()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("c47800c7266a2be04c571c04d5a6614691ea99bd");
+
+                Commit second = repo.Lookup<Commit>("9fd738e8f7967c078dceed8190330fc8648ee56a");
+
+                Commit ancestor = repo.Commits.FindCommonAncestor(new[] { first, second });
+
+                Assert.NotNull(ancestor);
+
+                ancestor.Id.Sha.ShouldEqual("5b5b025afb0b4c913b4c338a42934a3863bf3644");
+            }
+        }
+
+        [Fact]
+        public void CanCorrectlyFindCommonAncestorForSeveralCommits()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                Commit second = repo.Lookup<Commit>("be3563ae3f795b2b4353bcce3a527ad0a4f7f644");
+
+                Commit third = repo.Lookup<Commit>("c47800c7266a2be04c571c04d5a6614691ea99bd");
+
+                Commit fourth = repo.Lookup<Commit>("5b5b025afb0b4c913b4c338a42934a3863bf3644");
+
+                Commit ancestor = repo.Commits.FindCommonAncestor(new[] { first, second, third, fourth });
+
+                Assert.NotNull(ancestor);
+
+                ancestor.Id.Sha.ShouldEqual("5b5b025afb0b4c913b4c338a42934a3863bf3644");
+            }
+        }
+
+        [Fact]
+        public void CannotFindCommonAncestorForTwoCommmitsWithoutCommonAncestor()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                Commit second = repo.Lookup<Commit>("be3563ae3f795b2b4353bcce3a527ad0a4f7f644");
+
+                Commit third = repo.Lookup<Commit>("c47800c7266a2be04c571c04d5a6614691ea99bd");
+
+                Commit fourth = repo.Lookup<Commit>("5b5b025afb0b4c913b4c338a42934a3863bf3644");
+
+                // create new commit with no parents
+                TreeDefinition newTreeDef = TreeDefinition.From(first.Tree);
+                Tree newTree = repo.ObjectDatabase.CreateTree(newTreeDef);
+                Commit orphanedCommit = repo.ObjectDatabase.CreateCommit(
+                    "This is a test commit created by 'CommitFixture.CannotFindCommonAncestorForCommmitsWithoutCommonAncestor'",
+                    first.Author,
+                    first.Committer,
+                    newTree,
+                    Enumerable.Empty<Commit>());
+
+                Commit ancestor = repo.Commits.FindCommonAncestor(new[] { first, second, orphanedCommit, third, fourth });
+
+                Assert.Null(ancestor);
+            }
+        }
+
+        [Fact]
+        public void CannotFindCommonAncestorForSeveralCommmitsWithoutCommonAncestor()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                // create new commit with no parents
+                TreeDefinition newTreeDef = TreeDefinition.From(first.Tree);
+                Tree newTree = repo.ObjectDatabase.CreateTree(newTreeDef);
+                Commit orphanedCommit = repo.ObjectDatabase.CreateCommit(
+                    "This is a test commit created by 'CommitFixture.CannotFindCommonAncestorForCommmitsWithoutCommonAncestor'",
+                    first.Author,
+                    first.Committer,
+                    newTree,
+                    Enumerable.Empty<Commit>());
+
+                Commit ancestor = repo.Commits.FindCommonAncestor(first, orphanedCommit);
+
+                Assert.Null(ancestor);
+            }
+        }
+
+        public void FindCommonAncestorForSingleCommitThrows()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                Assert.Throws<ArgumentException>(() => repo.Commits.FindCommonAncestor(new[] { first }));
+            }
+        }
+
+        public void FindCommonAncestorForEnumerableWithNullCommitThrows()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                Commit second = repo.Lookup<Commit>("be3563ae3f795b2b4353bcce3a527ad0a4f7f644");
+
+                Assert.Throws<ArgumentException>(() => repo.Commits.FindCommonAncestor(new[] { first, second, null }));
+            }
+        }
+
+        public void FindCommonAncestorForWithNullCommitThrows()
+        {
+            using (var repo = new Repository(BareTestRepoPath))
+            {
+                Commit first = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+
+                Assert.Throws<ArgumentException>(() => repo.Commits.FindCommonAncestor(first, null));
+
+                Assert.Throws<ArgumentException>(() => repo.Commits.FindCommonAncestor(null, first));
+            }
+        }
+
         [Fact]
         public void CanEnumerateCommits()
         {

LibGit2Sharp/CommitCollection.cs

@@ -124,6 +124,61 @@ private static bool PointsAtTheHead(string shaOrRefName)
             return ("HEAD".Equals(shaOrRefName, StringComparison.Ordinal) || "refs/heads/master".Equals(shaOrRefName, StringComparison.Ordinal));
         }
 
+        /// <summary>
+        /// Find as good common ancestors as possible for a merge given two <see cref="Commit"/>.
+        /// </summary>
+        /// <param name="first">The first <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <param name="second">The second <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <returns>The common ancestor or null if none found.</returns>
+        public Commit FindCommonAncestor(Commit first, Commit second)
+        {
+            Ensure.ArgumentNotNull(first, "first");
+            Ensure.ArgumentNotNull(second, "second");
+            GitOid ret;
+            using (var osw1 = new ObjectSafeWrapper(first.Id, this.repo))
+            using (var osw2 = new ObjectSafeWrapper(second.Id, this.repo))
+            {
+                int result = NativeMethods.git_merge_base(out ret, this.repo.Handle, osw1.ObjectPtr, osw2.ObjectPtr);
+                if (result == (int)GitErrorCode.GIT_ENOTFOUND)
+                    return null;
+
+                Ensure.Success(result);
+                return this.repo.Lookup<Commit>(new ObjectId(ret));
+            }
+        }
+
+        /// <summary>
+        /// Find as good common ancestors as possible for a merge given two or more <see cref="Commit"/>.
+        /// </summary>
+        /// <param name="commits">The <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <returns>The common ancestor or null if none found.</returns>
+        public Commit FindCommonAncestor(IEnumerable<Commit> commits)
+        {
+            Ensure.ArgumentNotNull(commits, "commits");
+            Commit ret = null;
+            int count = 0;
+            foreach (var commit in commits)
+            {
+                if (commit == null)
+                    throw new ArgumentException("Enumerable contains null at position: " + count.ToString(CultureInfo.InvariantCulture), "commits");
+
+                count++;
+
+                if (ret == null)
+                    ret = commit;
+                else
+                {
+                    ret = this.FindCommonAncestor(ret, commit);
+                    if (ret == null)
+                        break;
+                }
+            }
+            if (count < 2)
+                throw new ArgumentException("The enumerable must contains at least two commits.", "commits");
+
+            return ret;
+        }
+
         /// <summary>
         ///   Stores the content of the <see cref = "Repository.Index" /> as a new <see cref = "Commit" /> into the repository.
         ///   The tip of the <see cref = "Repository.Head"/> will be used as the parent of this new Commit.

LibGit2Sharp/Core/NativeMethods.cs

@@ -326,6 +326,13 @@ public static extern int git_index_open(
         [DllImport(libgit2)]
         public static extern int git_index_write(IndexSafeHandle index);
 
+        [DllImport(libgit2)]
+        public static extern int git_merge_base(
+            out GitOid mergeBase,
+            RepositorySafeHandle repo,
+            GitObjectSafeHandle one,
+            GitObjectSafeHandle two);
+
         [DllImport(libgit2)]
         public static extern int git_odb_exists(ObjectDatabaseSafeHandle odb, ref GitOid id);
 

LibGit2Sharp/IQueryableCommitCollection.cs

@@ -1,4 +1,6 @@
-namespace LibGit2Sharp
+using System.Collections.Generic;
+
+namespace LibGit2Sharp
 {
     public interface IQueryableCommitCollection : ICommitCollection //TODO: Find a name that's more explicit than IQueryableCommitCollection
     {
@@ -20,5 +22,21 @@ public interface IQueryableCommitCollection : ICommitCollection //TODO: Find a n
         /// <param name = "amendPreviousCommit">True to amend the current <see cref = "Commit"/> pointed at by <see cref = "Repository.Head"/>, false otherwise.</param>
         /// <returns>The generated <see cref = "Commit" />.</returns>
         Commit Create(string message, Signature author, Signature committer, bool amendPreviousCommit);
+
+
+        /// <summary>
+        /// Find as good common ancestors as possible for a merge given two <see cref="Commit"/>.
+        /// </summary>
+        /// <param name="first">The first <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <param name="second">The second <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <returns>The common ancestor or null if none found.</returns>
+        Commit FindCommonAncestor(Commit first, Commit second);
+
+        /// <summary>
+        /// Find as good common ancestors as possible for a merge given two or more <see cref="Commit"/>.
+        /// </summary>
+        /// <param name="commits">The <see cref="Commit"/> for which to find the common ancestor.</param>
+        /// <returns>The common ancestor or null if none found.</returns>
+        Commit FindCommonAncestor(IEnumerable<Commit> commits);
     }
 }