Add support for ZDiff3 conflict resolution strategy in merge operations (#1976)

Author: DustinTheDev

LibGit2Sharp.Tests/MergeFixture.cs

@@ -669,6 +669,54 @@ public void CanSpecifyConflictFileStrategy(CheckoutFileConflictStrategy conflict
             }
         }
 
+        [Theory]
+        [InlineData(CheckoutFileConflictStrategy.Merge)]
+        [InlineData(CheckoutFileConflictStrategy.Diff3)]
+        [InlineData(CheckoutFileConflictStrategy.ZDiff3)]
+        public void CanSpecifyMergeConflictFileStrategy(CheckoutFileConflictStrategy conflictStrategy)
+        {
+            const string conflictFile = "a.txt";
+            const string expectedFileFormat = "a.{0}.txt";
+            const string conflictBranchName = "conflicts";
+            const string resultsBranchName = "results";
+
+            string expectedFileName = string.Format(expectedFileFormat, conflictStrategy.ToString().ToLower());
+            string path = SandboxMergeConflictTestRepo();
+
+            using (var repo = new Repository(path))
+            {
+                Branch branch = repo.Branches[conflictBranchName];
+                Assert.NotNull(branch);
+
+                // Ensure the working directory is clean before merging
+                repo.Reset(ResetMode.Hard);
+                repo.RemoveUntrackedFiles();
+
+                MergeOptions mergeOptions = new MergeOptions()
+                {
+                    FileConflictStrategy = conflictStrategy
+                };
+
+                MergeResult result = repo.Merge(branch, Constants.Signature, mergeOptions);
+                Assert.Equal(MergeStatus.Conflicts, result.Status);
+
+                // Get the information on the conflict.
+                Conflict conflict = repo.Index.Conflicts[conflictFile];
+
+                Assert.NotNull(conflict);
+                Assert.NotNull(conflict.Theirs);
+                Assert.NotNull(conflict.Ours);
+
+                Commit expectedCommit = repo.Branches[resultsBranchName].Tip;
+                Blob expectedBlob = (Blob)expectedCommit[expectedFileName].Target;
+                string expectedContent = expectedBlob.GetContentText(new FilteringOptions(expectedFileName));
+
+                // Verify the content of the file on disk contains conflict markers.
+                string fileContent = File.ReadAllText(Path.Combine(repo.Info.WorkingDirectory, conflictFile));
+                Assert.Equal(expectedContent, fileContent);
+            }
+        }
+
         [Theory]
         [InlineData(MergeFileFavor.Ours)]
         [InlineData(MergeFileFavor.Theirs)]

LibGit2Sharp.Tests/Resources/mergeconflict_testrepo_wd/a.txt

@@ -0,0 +1,7 @@
+A
+B
+C
+D
+E
+F
+G

LibGit2Sharp.Tests/Resources/mergeconflict_testrepo_wd/dot_git/HEAD

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

LibGit2Sharp.Tests/Resources/mergeconflict_testrepo_wd/dot_git/config

@@ -0,0 +1,6 @@
+[core]
+	repositoryformatversion = 0
+	filemode = false
+	bare = false
+	logallrefupdates = true
+	ignorecase = true

LibGit2Sharp.Tests/Resources/mergeconflict_testrepo_wd/dot_git/index

@@ -0,0 +1,3 @@
+cd4b13da8859445f4357c1e24d92b483ffe2dc85	refs/heads/conflicts
+0076e9fe99d1c2df56cd939a897db42d714b088b	refs/heads/main
+139641856b0ef7941f583972614c1df9bb26939b	refs/heads/results

LibGit2Sharp.Tests/Resources/mergeconflict_testrepo_wd/dot_git/info/refs

@@ -0,0 +1,3 @@
+P pack-5fd168964fc34fdc1e4a50ae098e21799dd906a4.pack
+P pack-9ea8f8acf571abc3f715ea91223671d542aacb6c.pack
+