feat(merge): read conflict stages and write user resolutions

src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs

@@ -23,6 +23,16 @@ public sealed record MergePreviewResult(
     IReadOnlyList<string> ConflictFiles,
     int ChangedFileCount);
 
+public sealed record MergeConflicts(
+    string TaskId,
+    IReadOnlyList<ConflictFileContent> Files);
+
+public sealed record ConflictFileContent(
+    string Path,
+    string Ours,
+    string Theirs,
+    string? Base);
+
 public sealed class TaskMergeService
 {
     public const string StatusMerged   = "merged";
@@ -217,6 +227,35 @@ public sealed class TaskMergeService
         return new MergeResult(StatusAborted, Array.Empty<string>(), null);
     }
 
+    public async Task<MergeConflicts> GetConflictsAsync(string taskId, CancellationToken ct)
+    {
+        var (_, list, _) = await LoadMergeContextAsync(taskId, ct);
+        if (string.IsNullOrWhiteSpace(list.WorkingDir))
+            throw new InvalidOperationException("list has no working directory");
+
+        var files = await _git.ListConflictedFilesAsync(list.WorkingDir, ct);
+        var result = new List<ConflictFileContent>(files.Count);
+        foreach (var path in files)
+        {
+            var ours   = await _git.ShowStageAsync(list.WorkingDir, 2, path, ct) ?? "";
+            var theirs = await _git.ShowStageAsync(list.WorkingDir, 3, path, ct) ?? "";
+            var @base  = await _git.ShowStageAsync(list.WorkingDir, 1, path, ct);
+            result.Add(new ConflictFileContent(path, ours, theirs, @base));
+        }
+        return new MergeConflicts(taskId, result);
+    }
+
+    public async Task WriteResolutionAsync(string taskId, string path, string content, CancellationToken ct)
+    {
+        var (_, list, _) = await LoadMergeContextAsync(taskId, ct);
+        if (string.IsNullOrWhiteSpace(list.WorkingDir))
+            throw new InvalidOperationException("list has no working directory");
+
+        var full = Path.Combine(list.WorkingDir, path.Replace('/', Path.DirectorySeparatorChar));
+        await File.WriteAllTextAsync(full, content, ct);
+        await _git.AddPathAsync(list.WorkingDir, path, ct);
+    }
+
     public async Task<MergeTargets> GetTargetsAsync(string taskId, CancellationToken ct)
     {
         var (_, list, _) = await LoadMergeContextAsync(taskId, ct);

tests/ClaudeDo.Worker.Tests/Services/TaskMergeServiceTests.cs

@@ -621,6 +621,72 @@ public class TaskMergeServiceTests : IDisposable
         // Cleanup
         GitRepoFixture.RunGit(repo.RepoDir, "merge", "--abort");
     }
+    [Fact]
+    public async Task GetConflictsAsync_AfterConflictMerge_ReturnsOursAndTheirs()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+        File.WriteAllText(Path.Combine(repo.RepoDir, "README.md"), "# main change\n");
+        GitRepoFixture.RunGit(repo.RepoDir, "commit", "-am", "main change");
+
+        var wtPath = Path.Combine(Path.GetTempPath(), $"wt_{Guid.NewGuid():N}");
+        _wtCleanups.Add((repo.RepoDir, wtPath));
+        GitRepoFixture.RunGit(repo.RepoDir, "worktree", "add", "-b", "claudedo/c1", wtPath, repo.BaseCommit);
+        File.WriteAllText(Path.Combine(wtPath, "README.md"), "# branch change\n");
+        GitRepoFixture.RunGit(wtPath, "commit", "-am", "branch change");
+
+        var (_, task) = await SeedListAndTask(db, workingDir: repo.RepoDir, status: TaskStatus.WaitingForReview);
+        await SeedWorktree(db, task.Id, wtPath, "claudedo/c1", repo.BaseCommit);
+
+        var (svc, _) = BuildService(db);
+        var start = await svc.MergeAsync(task.Id, "main", false, "msg", leaveConflictsInTree: true, CancellationToken.None);
+        Assert.Equal(TaskMergeService.StatusConflict, start.Status);
+
+        var conflicts = await svc.GetConflictsAsync(task.Id, CancellationToken.None);
+
+        Assert.Equal(task.Id, conflicts.TaskId);
+        var file = Assert.Single(conflicts.Files);
+        Assert.Equal("README.md", file.Path);
+        Assert.Contains("main change", file.Ours);
+        Assert.Contains("branch change", file.Theirs);
+        Assert.NotNull(file.Base);
+
+        GitRepoFixture.RunGit(repo.RepoDir, "merge", "--abort");
+    }
+
+    [Fact]
+    public async Task WriteResolutionAsync_ThenContinue_CompletesMerge()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+        File.WriteAllText(Path.Combine(repo.RepoDir, "README.md"), "# main change\n");
+        GitRepoFixture.RunGit(repo.RepoDir, "commit", "-am", "main change");
+
+        var wtPath = Path.Combine(Path.GetTempPath(), $"wt_{Guid.NewGuid():N}");
+        _wtCleanups.Add((repo.RepoDir, wtPath));
+        GitRepoFixture.RunGit(repo.RepoDir, "worktree", "add", "-b", "claudedo/c2", wtPath, repo.BaseCommit);
+        File.WriteAllText(Path.Combine(wtPath, "README.md"), "# branch change\n");
+        GitRepoFixture.RunGit(wtPath, "commit", "-am", "branch change");
+
+        var (_, task) = await SeedListAndTask(db, workingDir: repo.RepoDir, status: TaskStatus.WaitingForReview);
+        await SeedWorktree(db, task.Id, wtPath, "claudedo/c2", repo.BaseCommit);
+
+        var (svc, _) = BuildService(db);
+        await svc.MergeAsync(task.Id, "main", false, "msg", leaveConflictsInTree: true, CancellationToken.None);
+
+        await svc.WriteResolutionAsync(task.Id, "README.md", "# resolved by user\n", CancellationToken.None);
+        var result = await svc.ContinueMergeAsync(task.Id, CancellationToken.None);
+
+        Assert.Equal(TaskMergeService.StatusMerged, result.Status);
+        Assert.Equal("# resolved by user\n", File.ReadAllText(Path.Combine(repo.RepoDir, "README.md")));
+        Assert.False(await new GitService().IsMidMergeAsync(repo.RepoDir));
+    }
 }
 
 #region Test doubles