Added FindMergeBases on the ObjectDatabase class, equivalent to git merge-base --all.

LibGit2Sharp.Tests/CommitAncestorFixture.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using LibGit2Sharp.Tests.TestHelpers;
 using Xunit;
 using Xunit.Extensions;
@@ -8,6 +10,8 @@ namespace LibGit2Sharp.Tests
 {
     public class CommitAncestorFixture : BaseFixture
     {
+        private static int orphans;
+
         /*
          * BareTestRepoPath structure
          *
@@ -27,7 +31,7 @@ public class CommitAncestorFixture : BaseFixture
          *  |
          *  * commit 8496071c1b46c854b31185ea97743be6a877447
          *
-        */
+         */
 
         [Theory]
         [InlineData("5b5b025afb0b4c913b4c338a42934a3863bf3644", "c47800c", "9fd738e")]
@@ -85,6 +89,24 @@ public void FindCommonAncestorForCommitsAsEnumerable(string result, string[] sha
             }
         }
 
+        [Theory]
+        [InlineData(new[] { "0350717031bebea6b2600b89a33159935541cee1", "ebc932c47f8800bffdd150c560e111d87bb74f4f" }, new[] { "152325a", "c9a2051" })]
+        [InlineData(new[] { "0350717031bebea6b2600b89a33159935541cee1", "ebc932c47f8800bffdd150c560e111d87bb74f4f" }, new[] { "152325a", "c9a2051", "-" })]
+        [InlineData(new string[0], new[] { "-", "-" })]
+        public void FindCommonAncestorsForCommitsAsEnumerable(string[] results, string[] shas)
+        {
+            string path = SandboxCrossHistoryRepo();
+            using (var repo = new Repository(path))
+            {
+                var commits = shas.Select(sha => sha == "-" ? CreateOrphanedCommit(repo) : repo.Lookup<Commit>(sha)).ToArray();
+
+                var ancestors = repo.ObjectDatabase.FindMergeBases(commits).ToArray();
+
+                Assert.NotNull(ancestors);
+                Assert.Equal(results, ancestors.Select(a => a.Id.Sha));
+            }
+        }
+
         [Theory]
         [InlineData("4c062a6", "0000000")]
         [InlineData("0000000", "4c062a6")]
@@ -123,7 +145,7 @@ private static Commit CreateOrphanedCommit(IRepository repo)
             Commit orphanedCommit = repo.ObjectDatabase.CreateCommit(
                 random.Author,
                 random.Committer,
-                "This is a test commit created by 'CommitFixture.CannotFindCommonAncestorForCommmitsWithoutCommonAncestor'",
+                string.Format("This is a test commit (#{0}) created by 'CommitFixture.CannotFindCommonAncestorForCommmitsWithoutCommonAncestor'", Interlocked.Increment(ref orphans)),
                 random.Tree,
                 Enumerable.Empty<Commit>(),
                 false);

LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/a

LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/config

@@ -0,0 +1,8 @@
+[core]
+	repositoryformatversion = 0
+	filemode = false
+	bare = false
+	logallrefupdates = true
+	symlinks = false
+	ignorecase = true
+	hideDotFiles = dotGitOnly

LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/objects/eb/c932c47f8800bffdd150c560e111d87bb74f4f

@@ -0,0 +1,2 @@
+x
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+�@@]�)r
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LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/refs/heads/a

@@ -0,0 +1 @@
+152325a8a96b610627aaae41a00391c3644079e4

LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/refs/heads/b

@@ -0,0 +1 @@
+c9a20513b0648832b41b0f875ab16c92e4b7dae7

LibGit2Sharp.Tests/Resources/crosshistory_wd/dot_git/refs/heads/master

@@ -0,0 +1 @@
+a69878c70d9cce9a1fbec1712d1fcd4f609e689b

LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs

@@ -30,6 +30,7 @@ static BaseFixture()
         }
 
         public static string BareTestRepoPath { get; private set; }
+        public static string CrossHistoryRepoWorkingDirPath { get; private set; }
         public static string StandardTestRepoWorkingDirPath { get; private set; }
         public static string StandardTestRepoPath { get; private set; }
         public static string ShallowTestRepoPath { get; private set; }
@@ -63,6 +64,7 @@ private static void SetUpTestEnvironment()
 
             // Setup standard paths to our test repositories
             BareTestRepoPath = Path.Combine(sourceRelativePath, "testrepo.git");
+            CrossHistoryRepoWorkingDirPath = Path.Combine(sourceRelativePath, "crosshistory_wd");
             StandardTestRepoWorkingDirPath = Path.Combine(sourceRelativePath, "testrepo_wd");
             StandardTestRepoPath = Path.Combine(StandardTestRepoWorkingDirPath, "dot_git");
             ShallowTestRepoPath = Path.Combine(sourceRelativePath, "shallow.git");
@@ -131,6 +133,11 @@ protected string SandboxBareTestRepo()
             return Sandbox(BareTestRepoPath);
         }
 
+        protected string SandboxCrossHistoryRepo()
+        {
+            return Sandbox(CrossHistoryRepoWorkingDirPath);
+        }
+
         protected string SandboxStandardTestRepo()
         {
             return Sandbox(StandardTestRepoWorkingDirPath);

LibGit2Sharp/Core/GitOidArray.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace LibGit2Sharp.Core
+{
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct GitOidArray
+    {
+        /// <summary>
+        /// A pointer to an array of ids.
+        /// </summary>
+        public IntPtr Ids;
+
+        /// <summary>
+        /// The number of ids in the array.
+        /// </summary>
+        public UIntPtr Length;
+
+        /// <summary>
+        /// Resets the GitOidArray to default values.
+        /// </summary>
+        public void Reset()
+        {
+            Ids = IntPtr.Zero;
+            Length = UIntPtr.Zero;
+        }
+    }
+}

LibGit2Sharp/Core/GitOidArrayNative.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace LibGit2Sharp.Core
+{
+    /// <summary>
+    /// A git_oidarray where the id array and ids themselves were allocated
+    /// with libgit2's allocator. Only libgit2 can free this git_oidarray.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    internal class GitOidArrayNative : IDisposable
+    {
+        public GitOidArray Array;
+
+        /// <summary>
+        /// Reads each GitOid from the array.
+        /// </summary>
+        public GitOid[] ReadOids()
+        {
+            var count = checked((int)Array.Length.ToUInt32());
+
+            GitOid[] toReturn = new GitOid[count];
+
+            for (int i = 0; i < count; i++)
+            {
+                toReturn[i] = (Array.Ids + i * Marshal.SizeOf(typeof(GitOid))).MarshalAs<GitOid>();
+            }
+
+            return toReturn;
+        }
+
+        public void Dispose()
+        {
+            if (Array.Ids != IntPtr.Zero)
+            {
+                NativeMethods.git_oidarray_free(ref Array);
+            }
+
+            // Now that we've freed the memory, zero out the structure.
+            Array.Reset();
+        }
+    }
+}

LibGit2Sharp/Core/NativeMethods.cs

@@ -714,13 +714,24 @@ internal static extern int git_merge_base_many(
             int length,
             [In] GitOid[] input_array);
 
+        [DllImport(libgit2)]
+        internal static extern int git_merge_bases_many(
+            out GitOidArray mergeBases,
+            RepositorySafeHandle repo,
+            int length,
+            [In] GitOid[] input_array);
+
         [DllImport(libgit2)]
         internal static extern int git_merge_base_octopus(
             out GitOid mergeBase,
             RepositorySafeHandle repo,
             int length,
             [In] GitOid[] input_array);
 
+        [DllImport(libgit2)]
+        internal static extern void git_oidarray_free(
+            ref GitOidArray array);
+
         [DllImport(libgit2)]
         internal static extern int git_annotated_commit_from_ref(
             out GitAnnotatedCommitHandle annotatedCommit,

LibGit2Sharp/Core/Proxy.cs

@@ -1126,6 +1126,29 @@ public static ObjectId git_merge_base_many(RepositorySafeHandle repo, GitOid[] c
             return ret;
         }
 
+        public static ObjectId[] git_merge_bases_many(RepositorySafeHandle repo, GitOid[] commitIds)
+        {
+            var array = new GitOidArrayNative();
+
+            try
+            {
+                int res = NativeMethods.git_merge_bases_many(out array.Array, repo, commitIds.Length, commitIds);
+
+                if (res == (int)GitErrorCode.NotFound)
+                {
+                    return new ObjectId[0];
+                }
+
+                Ensure.ZeroResult(res);
+
+                return Array.ConvertAll(array.ReadOids(), id => (ObjectId)id);
+            }
+            finally
+            {
+                array.Dispose();
+            }
+        }
+
         public static ObjectId git_merge_base_octopus(RepositorySafeHandle repo, GitOid[] commitIds)
         {
             GitOid ret;

LibGit2Sharp/LibGit2Sharp.csproj

@@ -71,6 +71,8 @@
     <Compile Include="CompareOptions.cs" />
     <Compile Include="Core\FileHistory.cs" />
     <Compile Include="Core\GitFetchOptions.cs" />
+    <Compile Include="Core\GitOidArray.cs" />
+    <Compile Include="Core\GitOidArrayNative.cs" />
     <Compile Include="Core\GitPushUpdate.cs" />
     <Compile Include="Core\GitSubmoduleIgnore.cs" />
     <Compile Include="Core\Platform.cs" />

LibGit2Sharp/ObjectDatabase.cs

@@ -586,6 +586,38 @@ public virtual Commit FindMergeBase(IEnumerable<Commit> commits, MergeBaseFindin
             return id == null ? null : repo.Lookup<Commit>(id);
         }
 
+        /// <summary>
+        /// Find all best possible merge bases given two or more <see cref="Commit"/>.
+        /// </summary>
+        /// <param name="commits">The <see cref="Commit"/>s for which to find the merge bases.</param>
+        /// <returns>An enumerable collection containing all best possible merge bases.</returns>
+        public virtual IEnumerable<Commit> FindMergeBases(IEnumerable<Commit> commits)
+        {
+            Ensure.ArgumentNotNull(commits, "commits");
+
+            List<GitOid> ids = new List<GitOid>(8);
+            int count = 0;
+
+            foreach (var commit in commits)
+            {
+                if (commit == null)
+                {
+                    throw new ArgumentException("Enumerable contains null at position: " + count.ToString(CultureInfo.InvariantCulture), "commits");
+                }
+                ids.Add(commit.Id.Oid);
+                count++;
+            }
+
+            if (count < 2)
+            {
+                throw new ArgumentException("The enumerable must contains at least two commits.", "commits");
+            }
+
+            var baseIds = Proxy.git_merge_bases_many(repo.Handle, ids.ToArray());
+
+            return baseIds.Select(id => repo.Lookup<Commit>(id)).ToList();
+        }
+
         /// <summary>
         /// Perform a three-way merge of two commits, looking up their
         /// commit ancestor. The returned index will contain the results