From 1502b9332525a8047f1340c67cd0e85e1485083c Mon Sep 17 00:00:00 2001
From: Julien Richard <julien.richard@ubisoft.com>
Date: Mon, 3 Jan 2022 16:15:59 +0100
Subject: [PATCH 1/3] Throw NotFoundException if trees are missing when
 computing diff

---
 LibGit2Sharp/Core/Proxy.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/LibGit2Sharp/Core/Proxy.cs b/LibGit2Sharp/Core/Proxy.cs
index 6c6d04670..8991430bd 100644
--- a/LibGit2Sharp/Core/Proxy.cs
+++ b/LibGit2Sharp/Core/Proxy.cs
@@ -797,8 +797,8 @@ public static unsafe DiffHandle git_diff_tree_to_tree(
             ObjectId newTree,
             GitDiffOptions options)
         {
-            using (var osw1 = new ObjectSafeWrapper(oldTree, repo, true))
-            using (var osw2 = new ObjectSafeWrapper(newTree, repo, true))
+            using (var osw1 = new ObjectSafeWrapper(oldTree, repo, true, throwIfMissing: true))
+            using (var osw2 = new ObjectSafeWrapper(newTree, repo, true, throwIfMissing: true))
             {
                 git_diff* diff;
                 int res = NativeMethods.git_diff_tree_to_tree(out diff, repo, osw1.ObjectPtr, osw2.ObjectPtr, options);

From 93d8e453c7f8698cdbdd126da981e64c51689c96 Mon Sep 17 00:00:00 2001
From: Julien Richard <julien.richard@ubisoft.com>
Date: Mon, 3 Jan 2022 18:10:54 +0100
Subject: [PATCH 2/3] Add test

---
 LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs | 35 +++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs b/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
index d03b26e4e..e2760757b 100644
--- a/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
+++ b/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
@@ -1256,5 +1256,40 @@ public void UsingPatienceAlgorithmCompareOptionProducesPatienceDiff()
                     Assert.Equal(diffPatience, changes);
             }
         }
+
+        [Fact]
+        public void DiffThrowsANotFoundExceptionIfATreeIsMissing()
+        {
+            string repoPath = SandboxBareTestRepo();
+
+            // Manually delete the objects directory to simulate a partial clone
+            File.Delete(Path.Combine(repoPath, "objects", "58", "1f9824ecaf824221bd36edf5430f2739a7c4f5")); 
+
+            using (var repo = new Repository(repoPath))
+            {
+                // The commit is there but its tree is missing
+                var commit = repo.Lookup<Commit>("4c062a6361ae6959e06292c1fa5e2822d9c96345");
+                Assert.NotNull(commit);
+                Assert.Equal("581f9824ecaf824221bd36edf5430f2739a7c4f5", commit.Tree.Sha);
+                Assert.True(commit.Tree.IsMissing);
+
+                var tree = repo.Lookup<Tree>("581f9824ecaf824221bd36edf5430f2739a7c4f5");
+                Assert.Null(tree);
+
+                var otherCommit = repo.Lookup<Commit>("be3563ae3f795b2b4353bcce3a527ad0a4f7f644");
+                Assert.NotNull(otherCommit);
+                Assert.False(otherCommit.Tree.IsMissing);
+
+                Assert.Throws<NotFoundException>(() =>
+                {
+                    using (repo.Diff.Compare<TreeChanges>(commit.Tree, otherCommit.Tree)) {}
+                });
+
+                Assert.Throws<NotFoundException>(() =>
+                {
+                    using (repo.Diff.Compare<TreeChanges>(otherCommit.Tree, commit.Tree)) {}
+                });
+            }
+        }
     }
 }

From 9780ddf9450ef6c740bce21a20d8e0765116fcbe Mon Sep 17 00:00:00 2001
From: Julien Richard <julien.richard@ubisoft.com>
Date: Mon, 3 Jan 2022 19:40:27 +0100
Subject: [PATCH 3/3] Fix comment

---
 LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs b/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
index e2760757b..0fe7adee1 100644
--- a/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
+++ b/LibGit2Sharp.Tests/DiffTreeToTreeFixture.cs
@@ -1262,7 +1262,7 @@ public void DiffThrowsANotFoundExceptionIfATreeIsMissing()
         {
             string repoPath = SandboxBareTestRepo();
 
-            // Manually delete the objects directory to simulate a partial clone
+            // Manually delete the tree object to simulate a partial clone
             File.Delete(Path.Combine(repoPath, "objects", "58", "1f9824ecaf824221bd36edf5430f2739a7c4f5")); 
 
             using (var repo = new Repository(repoPath))