fix(claude-do): merge Modify/Delete- und Rename-Konflikte im Merge sichtbar machen

ClaudeDo-Task: 059bcf98-34d5-4ca0-822d-317980fadf8d

src/ClaudeDo.Data/Git/GitService.cs

@@ -376,6 +376,32 @@ public sealed class GitService
             throw new InvalidOperationException($"git add '{path}' failed (exit {exitCode}): {stderr}");
     }
 
+    /// <summary>
+    /// Stages <paramref name="path"/> as deleted (`git rm -f`), removing it from both the index
+    /// and, if present, the working tree. Used to resolve a merge conflict to "keep the
+    /// deletion" — unlike <see cref="AddPathAsync"/>, which would stage an empty file as a
+    /// tracked, zero-byte file rather than actually removing it.
+    /// </summary>
+    public async Task RemovePathAsync(string repoDir, string path, CancellationToken ct = default)
+    {
+        var (exitCode, _, stderr) = await RunGitAsync(repoDir, ["rm", "-f", "--", path], ct);
+        if (exitCode != 0)
+            throw new InvalidOperationException($"git rm '{path}' failed (exit {exitCode}): {stderr}");
+    }
+
+    /// <summary>
+    /// Content of <paramref name="path"/> at a merge stage (1=base, 2=ours, 3=theirs) via
+    /// `git show :&lt;stage&gt;:&lt;path&gt;`. Null when that stage doesn't exist for the path —
+    /// the conventional way to tell a modify/delete or rename/delete conflict apart from an
+    /// ordinary content conflict (git never writes `&lt;&lt;&lt;&lt;&lt;&lt;&lt;` markers for those,
+    /// it just leaves whichever side wasn't deleted in the working tree).
+    /// </summary>
+    public async Task<string?> ShowConflictStageAsync(string repoDir, int stage, string path, CancellationToken ct = default)
+    {
+        var (exitCode, stdout, _) = await RunGitAsync(repoDir, ["show", $":{stage}:{path}"], ct, trimOutput: false);
+        return exitCode == 0 ? stdout : null;
+    }
+
     /// <summary>
     /// Non-destructive mergeability probe via `git merge-tree --write-tree`. Writes only
     /// loose objects — the working tree, index, and refs are left untouched.

src/ClaudeDo.Worker/Lifecycle/TaskMergeService.cs

@@ -545,20 +545,48 @@ public sealed class TaskMergeService
             var oldTargetTip = await _git.RevParseHeadAsync(list.WorkingDir, ct);
 
             // Validate BEFORE staging: `git add` marks a conflicted path resolved regardless of
-            // its content, so an unresolved file with markers still in it would otherwise get
+            // its content, so an unresolved file needs a positively-checked resolution, not just
-            // staged (and committed) as-is. Check text content for markers first; binary files
+            // "whatever happens to be on disk". For an ordinary content conflict, git always
-            // can't carry markers, so they're left to the post-stage index check below.
+            // starts the file with markers, so their absence reliably means someone resolved it
+            // (in-app or in an external editor). A modify/delete or rename/delete conflict never
+            // gets markers at all (GetConflictDocumentsAsync) — the same marker-less state also
+            // describes a file nobody has touched — so those are additionally checked against
+            // what git itself left on disk by default (whichever side wasn't deleted); still
+            // matching that default means still unresolved.
             var unresolved = await _git.ListConflictedFilesAsync(list.WorkingDir, ct);
             var stillConflicted = new List<string>();
+            var toAdd = new List<string>();
+            var toRemove = new List<string>();
             foreach (var path in unresolved)
             {
                 var full = Path.Combine(list.WorkingDir, path.Replace('/', Path.DirectorySeparatorChar));
-                string text;
+                string? text = null;
-                try { text = await File.ReadAllTextAsync(full, ct); }
+                if (File.Exists(full))
-                catch { continue; }
+                {
+                    try { text = await File.ReadAllTextAsync(full, ct); }
+                    catch { /* treated as unresolved below */ }
+                }
 
-                if (!LooksBinary(text) && ConflictMarkerParser.HasConflicts(text))
+                if (text is not null && (LooksBinary(text) || ConflictMarkerParser.HasConflicts(text)))
+                {
                     stillConflicted.Add(path);
+                    continue;
+                }
+
+                var oursStage = await _git.ShowConflictStageAsync(list.WorkingDir, 2, path, ct);
+                var theirsStage = await _git.ShowConflictStageAsync(list.WorkingDir, 3, path, ct);
+                var isModifyDeleteStyle = oursStage is null || theirsStage is null;
+                if (isModifyDeleteStyle &&
+                    NormalizeLineEndings(text ?? "") == NormalizeLineEndings(oursStage ?? theirsStage ?? ""))
+                {
+                    stillConflicted.Add(path);
+                    continue;
+                }
+
+                if (text is null || text.Length == 0)
+                    toRemove.Add(path);
+                else
+                    toAdd.Add(path);
             }
 
             if (stillConflicted.Count > 0)
@@ -575,8 +603,10 @@ public sealed class TaskMergeService
             // Stage exactly the resolved conflict paths — never `git add -A`, which would sweep
             // untracked/unrelated changes left by other sessions into this merge commit (the
             // target working dir is shared).
-            foreach (var path in unresolved)
+            foreach (var path in toAdd)
                 await _git.AddPathAsync(list.WorkingDir, path, ct);
+            foreach (var path in toRemove)
+                await _git.RemovePathAsync(list.WorkingDir, path, ct);
 
             var remaining = await _git.ListConflictedFilesAsync(list.WorkingDir, ct);
             if (remaining.Count > 0)
@@ -713,6 +743,15 @@ public sealed class TaskMergeService
     /// <summary>
     /// Reads each conflicted working-tree file and parses its conflict markers into line-level
     /// segments (with the diff3 merge base when present). Binary files are flagged and skipped.
+    /// A path with no text markers on disk is either an ordinary content conflict that's already
+    /// been resolved (git keeps both index stages until the path is staged, whether or not the
+    /// working tree still looks conflicted — reads as a single stable segment, 0 hunks left), or
+    /// a modify/delete or rename/delete conflict — git never writes markers for those at all, it
+    /// just leaves whichever side wasn't deleted sitting in the working tree, so the same
+    /// "no markers" state also describes an untouched file. The index tells the two apart: a
+    /// modify/delete-style conflict only ever populates ONE of the ours/theirs stages. Those are
+    /// synthesized into a single whole-file conflict block straight from the stages (empty side
+    /// = that side deleted the path) so the resolver still shows a real choice.
     /// </summary>
     public async Task<ConflictDocuments> GetConflictDocumentsAsync(string taskId, CancellationToken ct)
     {
@@ -725,21 +764,53 @@ public sealed class TaskMergeService
         foreach (var path in files)
         {
             var full = Path.Combine(list.WorkingDir, path.Replace('/', Path.DirectorySeparatorChar));
-            string text;
+            string? diskText = null;
-            try { text = await File.ReadAllTextAsync(full, ct); }
+            if (File.Exists(full))
-            catch { text = ""; }
+            {
+                try { diskText = await File.ReadAllTextAsync(full, ct); }
+                catch { /* unreadable — fall through to the index stages below */ }
+            }
 
-            if (LooksBinary(text))
+            if (diskText is not null && LooksBinary(diskText))
             {
                 result.Add(new ConflictDocumentContent(path, true, Array.Empty<MergeSegment>()));
                 continue;
             }
 
-            result.Add(new ConflictDocumentContent(path, false, ConflictMarkerParser.Parse(text)));
+            if (diskText is not null && ConflictMarkerParser.HasConflicts(diskText))
+            {
+                result.Add(new ConflictDocumentContent(path, false, ConflictMarkerParser.Parse(diskText)));
+                continue;
+            }
+
+            var ours = await _git.ShowConflictStageAsync(list.WorkingDir, 2, path, ct);
+            var theirs = await _git.ShowConflictStageAsync(list.WorkingDir, 3, path, ct);
+            if (ours is not null && theirs is not null)
+            {
+                // Ordinary two-sided conflict, already resolved (no markers left) but not yet staged.
+                result.Add(new ConflictDocumentContent(path, false,
+                    new[] { MergeSegment.Stable(diskText ?? "") }));
+                continue;
+            }
+
+            if (LooksBinary(ours ?? "") || LooksBinary(theirs ?? ""))
+            {
+                result.Add(new ConflictDocumentContent(path, true, Array.Empty<MergeSegment>()));
+                continue;
+            }
+
+            var @base = await _git.ShowConflictStageAsync(list.WorkingDir, 1, path, ct);
+            result.Add(new ConflictDocumentContent(
+                path, false, new[] { MergeSegment.Conflict(ours ?? "", @base, theirs ?? "") }));
         }
         return new ConflictDocuments(taskId, result);
     }
 
+    // Working-tree checkouts can go through autocrlf while `git show :stage:path` never does —
+    // normalize before comparing the two or an untouched file reads as "resolved" on a machine
+    // with autocrlf enabled.
+    private static string NormalizeLineEndings(string text) => text.Replace("\r\n", "\n").Replace('\r', '\n');
+
     // A NUL byte in the head of the file is the conventional binary sniff.
     private static bool LooksBinary(string text)
     {
@@ -755,6 +826,15 @@ public sealed class TaskMergeService
         if (string.IsNullOrWhiteSpace(list.WorkingDir))
             throw new InvalidOperationException("list has no working directory");
 
+        if (content.Length == 0)
+        {
+            // An empty resolution for a whole-file conflict (modify/delete, rename/delete) means
+            // "keep the deletion" — `git add` on an empty file would instead stage it as a
+            // tracked, zero-byte file, which is not what accepting the deleted side means.
+            await _git.RemovePathAsync(list.WorkingDir, path, ct);
+            return;
+        }
+
         var full = Path.Combine(list.WorkingDir, path.Replace('/', Path.DirectorySeparatorChar));
         await File.WriteAllTextAsync(full, content, ct);
         await _git.AddPathAsync(list.WorkingDir, path, ct);

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

@@ -1109,6 +1109,63 @@ public class TaskMergeServiceTests : IDisposable
         Assert.Contains(file.Segments, s => !s.IsConflict && s.Text.Contains("line1"));
     }
 
+    // git never writes <<<<<<< markers for a modify/delete conflict -- it just leaves the
+    // modifying side's content sitting in the working tree, which used to read as an
+    // already-resolved stable file (no conflict at all) to both GetConflictDocumentsAsync and
+    // ContinueMergeAsync's marker scan, so `continue_merge` would silently keep the modification.
+    [Fact]
+    public async Task ModifyDeleteConflict_IsSynthesizedAndCannotBeSilentlyStaged()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var db = NewDb();
+        var repo = NewRepo();
+        GitRepoFixture.RunGit(repo.RepoDir, "branch", "-m", "main");
+
+        var wtPath = Path.Combine(Path.GetTempPath(), $"wt_{Guid.NewGuid():N}");
+        _wtCleanups.Add((repo.RepoDir, wtPath));
+        GitRepoFixture.RunGit(repo.RepoDir, "worktree", "add", "-b", "claudedo/modify-delete", wtPath, repo.BaseCommit);
+        File.WriteAllText(Path.Combine(wtPath, "README.md"), "# modified by branch\n");
+        GitRepoFixture.RunGit(wtPath, "commit", "-am", "branch modifies README");
+
+        GitRepoFixture.RunGit(repo.RepoDir, "rm", "README.md");
+        GitRepoFixture.RunGit(repo.RepoDir, "commit", "-m", "main deletes README");
+
+        var (_, task) = await SeedListAndTask(db, workingDir: repo.RepoDir, status: TaskStatus.Done);
+        await SeedWorktree(db, task.Id, wtPath, "claudedo/modify-delete", repo.BaseCommit);
+
+        var (svc, _) = BuildService(db);
+        var merge = await svc.MergeAsync(task.Id, "main", removeWorktree: false, "msg",
+            leaveConflictsInTree: true, CancellationToken.None);
+        Assert.Equal(TaskMergeService.StatusConflict, merge.Status);
+
+        // No <<<<<<< markers anywhere -- git left the branch's modification as-is.
+        Assert.DoesNotContain("<<<<<<<", File.ReadAllText(Path.Combine(repo.RepoDir, "README.md")));
+
+        var docs = await svc.GetConflictDocumentsAsync(task.Id, CancellationToken.None);
+        var file = Assert.Single(docs.Files);
+        Assert.EndsWith("README.md", file.Path.Replace('\\', '/'));
+        Assert.False(file.IsBinary);
+        var conflict = Assert.Single(file.Segments.Where(s => s.IsConflict).ToList());
+        Assert.Equal("", conflict.Ours);                        // ours (main) deleted it
+        Assert.Contains("modified by branch", conflict.Theirs); // theirs (branch) modified it
+
+        // Nobody resolved it — continue must refuse rather than silently keeping the modification.
+        var headBefore = GitRepoFixture.RunGit(repo.RepoDir, "rev-parse", "HEAD").Trim();
+        var refused = await svc.ContinueMergeAsync(task.Id, CancellationToken.None);
+        Assert.Equal(TaskMergeService.StatusConflict, refused.Status);
+        Assert.Contains("README.md", refused.ConflictFiles);
+        Assert.Equal(headBefore, GitRepoFixture.RunGit(repo.RepoDir, "rev-parse", "HEAD").Trim());
+        Assert.True(await new GitService().IsMidMergeAsync(repo.RepoDir));
+
+        // Explicitly resolving to the deleted (ours) side must `git rm`, not stage an empty file.
+        await svc.WriteResolutionAsync(task.Id, "README.md", "", CancellationToken.None);
+        var result = await svc.ContinueMergeAsync(task.Id, CancellationToken.None);
+        Assert.Equal(TaskMergeService.StatusMerged, result.Status);
+        Assert.False(File.Exists(Path.Combine(repo.RepoDir, "README.md")));
+        Assert.False(await new GitService().IsMidMergeAsync(repo.RepoDir));
+    }
+
     [Fact]
     public async Task ApproveAndMergeAsync_NoWorktree_MarksDone()
     {