Add backup-first duplicate repair

docs/design/duplicate-repair.md

@@ -0,0 +1,39 @@
+# Duplicate repair
+
+## Problem
+
+Duplicate and cloud-conflict files waste space, but deleting either path can
+unmap tracks in crates or Serato's database. DJs need to choose the authoritative
+copy and understand every change before it happens.
+
+## Design
+
+The web interface requires an analysis, an explicit keeper selection, and a
+dry-run preview. Applying the plan first creates a timestamped backup beneath
+`_Serato_/.serato-doctor-backups/`. The snapshot contains every replaced audio
+file, loaded crate/smart-crate metadata, database V2, and a JSON restore manifest.
+
+The non-kept audio path is then replaced with a symbolic link to the keeper.
+This removes the extra audio payload while preserving every existing saved path.
+Crate files and database V2 are never rewritten. The UI exposes immediate
+restore using the manifest.
+
+Users may retain all backups or set a positive rotation limit. Rotation occurs
+only after a repair succeeds.
+
+## Edge cases
+
+- The duplicate group is rescanned and validated immediately before preview and
+  apply.
+- Existing symlinks cannot be selected as disposable duplicate files.
+- A partial failure restores already-changed files before reporting the error.
+- Restore refuses to overwrite a real file.
+- Healthy symlink aliases are excluded from future duplicate counts.
+
+## Tests
+
+- Backup creation includes audio and Serato metadata.
+- The old path resolves to the selected keeper after repair.
+- Restore returns the original file contents.
+- Invalid keeper choices are rejected.
+- Limited and unlimited retention behave deterministically.

serato_doctor/duplicates.py

@@ -11,7 +11,9 @@ def find_duplicate_groups(
 ) -> Tuple[DuplicateGroup, ...]:
     """Find exact-name duplicates and suspected numeric conflict copies."""
 
-    track_tuple = tuple(tracks)
+    # Healthy symlinks preserve legacy Serato paths without consuming another
+    # copy of the audio, so they are aliases rather than duplicate files.
+    track_tuple = tuple(track for track in tracks if not track.path.is_symlink())
     by_name: DefaultDict[str, List[DiskTrack]] = defaultdict(list)
     by_conflict_name: DefaultDict[str, List[DiskTrack]] = defaultdict(list)
 

serato_doctor/repair.py

@@ -0,0 +1,160 @@
+"""Backup-first duplicate consolidation.
+
+Serato's binary metadata is deliberately not rewritten.  Removed duplicate files
+are replaced with symbolic links, so every existing path continues to resolve.
+"""
+
+import json
+import shutil
+from dataclasses import dataclass
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Iterable, Optional, Tuple
+from uuid import uuid4
+
+
+BACKUP_FOLDER = ".serato-doctor-backups"
+
+
+@dataclass(frozen=True)
+class DuplicateRepairPlan:
+    keeper: Path
+    replaced: Tuple[Path, ...]
+    metadata_files: Tuple[Path, ...]
+
+    @property
+    def changes(self) -> int:
+        return len(self.replaced)
+
+
+@dataclass(frozen=True)
+class RepairReceipt:
+    backup: Path
+    keeper: Path
+    replaced: Tuple[Path, ...]
+
+
+def plan_duplicate_repair(
+    keeper: Path, duplicates: Iterable[Path], serato_root: Path
+) -> DuplicateRepairPlan:
+    keeper = keeper.expanduser().resolve()
+    candidates = tuple(path.expanduser().resolve() for path in duplicates)
+    if keeper not in candidates:
+        raise ValueError("The file to keep must belong to this duplicate group")
+    if not keeper.is_file():
+        raise ValueError(f"The file to keep no longer exists: {keeper}")
+    replaced = tuple(path for path in candidates if path != keeper)
+    if not replaced:
+        raise ValueError("Choose a duplicate group containing at least two files")
+    if any(not path.is_file() or path.is_symlink() for path in replaced):
+        raise ValueError("A duplicate changed since the analysis; analyze again")
+    metadata = tuple(
+        sorted(
+            path
+            for path in serato_root.expanduser().resolve().rglob("*")
+            if path.is_file()
+            and BACKUP_FOLDER not in path.parts
+            and (
+                path.name == "database V2"
+                or path.suffix.casefold() in {".crate", ".scrate"}
+            )
+        )
+    )
+    return DuplicateRepairPlan(keeper, replaced, metadata)
+
+
+def apply_duplicate_repair(
+    plan: DuplicateRepairPlan,
+    serato_root: Path,
+    backup_limit: Optional[int] = 10,
+) -> RepairReceipt:
+    """Create a complete rollback snapshot, then replace extras with symlinks."""
+    if backup_limit is not None and backup_limit < 1:
+        raise ValueError("Backup limit must be at least 1, or unlimited")
+    backup_root = serato_root.expanduser().resolve() / BACKUP_FOLDER
+    backup = backup_root / _backup_name()
+    files_root = backup / "files"
+    metadata_root = backup / "serato-metadata"
+    backup.mkdir(parents=True)
+
+    entries = []
+    try:
+        for path in plan.replaced:
+            destination = files_root / _safe_backup_path(path)
+            destination.parent.mkdir(parents=True, exist_ok=True)
+            shutil.copy2(path, destination)
+            entries.append({"original": str(path), "backup": str(destination)})
+        for path in plan.metadata_files:
+            relative = path.relative_to(serato_root.expanduser().resolve())
+            destination = metadata_root / relative
+            destination.parent.mkdir(parents=True, exist_ok=True)
+            shutil.copy2(path, destination)
+        manifest = {
+            "created_at": datetime.now(timezone.utc).isoformat(),
+            "keeper": str(plan.keeper),
+            "replaced": entries,
+            "strategy": "symlink",
+        }
+        (backup / "manifest.json").write_text(
+            json.dumps(manifest, indent=2), encoding="utf-8"
+        )
+        for path in plan.replaced:
+            path.unlink()
+            path.symlink_to(plan.keeper)
+    except Exception:
+        _rollback_entries(entries)
+        shutil.rmtree(backup, ignore_errors=True)
+        raise
+
+    rotate_backups(backup_root, backup_limit)
+    return RepairReceipt(backup, plan.keeper, plan.replaced)
+
+
+def restore_backup(backup: Path) -> Tuple[Path, ...]:
+    manifest_path = backup.expanduser().resolve() / "manifest.json"
+    manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
+    restored = []
+    for entry in manifest["replaced"]:
+        original = Path(entry["original"])
+        saved = Path(entry["backup"])
+        if original.exists() and not original.is_symlink():
+            raise ValueError(f"Restore would overwrite a real file: {original}")
+        if original.is_symlink():
+            original.unlink()
+        original.parent.mkdir(parents=True, exist_ok=True)
+        shutil.copy2(saved, original)
+        restored.append(original)
+    return tuple(restored)
+
+
+def rotate_backups(backup_root: Path, limit: Optional[int]) -> None:
+    if limit is None or not backup_root.is_dir():
+        return
+    backups = sorted(
+        (path for path in backup_root.iterdir() if (path / "manifest.json").is_file()),
+        key=lambda path: path.name,
+        reverse=True,
+    )
+    for expired in backups[limit:]:
+        shutil.rmtree(expired)
+
+
+def _backup_name() -> str:
+    stamp = datetime.now(timezone.utc).strftime("%Y%m%dT%H%M%SZ")
+    return f"{stamp}-{uuid4().hex[:8]}"
+
+
+def _safe_backup_path(path: Path) -> Path:
+    anchorless = path.as_posix().lstrip("/").replace(":", "_")
+    return Path(anchorless)
+
+
+def _rollback_entries(entries: Iterable[dict]) -> None:
+    for entry in entries:
+        original = Path(entry["original"])
+        saved = Path(entry["backup"])
+        if original.is_symlink():
+            original.unlink()
+        if not original.exists() and saved.is_file():
+            original.parent.mkdir(parents=True, exist_ok=True)
+            shutil.copy2(saved, original)

serato_doctor/web.py

@@ -5,7 +5,7 @@ from dataclasses import asdict
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 from importlib import resources
 from pathlib import Path
-from typing import Iterable
+from typing import Iterable, Optional
 
 from serato_doctor.crate_parser import load_library_crates
 from serato_doctor.database_parser import parse_database
@@ -16,6 +16,12 @@ from serato_doctor.models.crate import CrateKind
 from serato_doctor.models.duplicate import DuplicateKind
 from serato_doctor.models.library import Library
 from serato_doctor.scanner import scan_filesystem
+from serato_doctor.repair import (
+    BACKUP_FOLDER,
+    apply_duplicate_repair,
+    plan_duplicate_repair,
+    restore_backup,
+)
 
 
 MAX_REQUEST_BYTES = 64 * 1024
@@ -225,6 +231,44 @@ def analyze_paths(
     return result
 
 
+def duplicate_repair(
+    serato: Path,
+    music: Path,
+    keeper: Path,
+    group_files: Iterable[Path],
+    backup_limit: Optional[int],
+    apply: bool = False,
+) -> dict:
+    """Validate a current duplicate group and preview or apply consolidation."""
+    serato = serato.expanduser().resolve()
+    music = music.expanduser().resolve()
+    keeper = keeper.expanduser().resolve()
+    requested = tuple(path.expanduser().resolve() for path in group_files)
+    if not serato.is_dir() or not music.is_dir():
+        raise ValueError("Analyze the library again before repairing duplicates")
+    tracks = scan_filesystem(music).tracks
+    groups = find_duplicate_groups(tracks)
+    valid_groups = [
+        {track.path.resolve() for track in group.tracks} for group in groups
+    ]
+    if set(requested) not in valid_groups:
+        raise ValueError("This duplicate group changed; analyze the library again")
+    plan = plan_duplicate_repair(keeper, requested, serato)
+    result = {
+        "keeper": str(plan.keeper),
+        "replaced": [str(path) for path in plan.replaced],
+        "metadata_backups": len(plan.metadata_files),
+        "strategy": "shortcut",
+        "database_v2_modified": False,
+    }
+    if apply:
+        receipt = apply_duplicate_repair(plan, serato, backup_limit)
+        result.update({"applied": True, "backup": str(receipt.backup)})
+    else:
+        result["applied"] = False
+    return result
+
+
 class SeratoDoctorHandler(BaseHTTPRequestHandler):
     def do_GET(self) -> None:
         asset = STATIC_FILES.get(self.path)
@@ -244,7 +288,13 @@ class SeratoDoctorHandler(BaseHTTPRequestHandler):
         self.wfile.write(content)
 
     def do_POST(self) -> None:
-        if self.path != "/api/analyze":
+        allowed = {
+            "/api/analyze",
+            "/api/duplicates/preview",
+            "/api/duplicates/apply",
+            "/api/backups/restore",
+        }
+        if self.path not in allowed:
             self._json_response(404, {"error": "Not found"})
             return
         try:
@@ -254,11 +304,37 @@ class SeratoDoctorHandler(BaseHTTPRequestHandler):
             payload = json.loads(self.rfile.read(length))
             if not isinstance(payload, dict):
                 raise ValueError("Request body must be a JSON object")
-            roots = [Path(value) for value in payload.get("reference_roots", [])]
-            result = analyze_paths(
-                Path(payload["serato"]), Path(payload["music"]), roots
-            )
-        except (KeyError, TypeError, json.JSONDecodeError, ValueError) as error:
+            if self.path == "/api/analyze":
+                roots = [Path(value) for value in payload.get("reference_roots", [])]
+                result = analyze_paths(
+                    Path(payload["serato"]), Path(payload["music"]), roots
+                )
+            elif self.path == "/api/backups/restore":
+                serato = Path(payload["serato"]).expanduser().resolve()
+                backup = Path(payload["backup"]).expanduser().resolve()
+                backup_root = (serato / BACKUP_FOLDER).resolve()
+                if backup.parent != backup_root:
+                    raise ValueError("That backup does not belong to this library")
+                restored = restore_backup(backup)
+                result = {"restored": [str(path) for path in restored]}
+            else:
+                raw_limit = payload.get("backup_limit", 10)
+                backup_limit = None if raw_limit is None else int(raw_limit)
+                result = duplicate_repair(
+                    Path(payload["serato"]),
+                    Path(payload["music"]),
+                    Path(payload["keeper"]),
+                    (Path(value) for value in payload["group_files"]),
+                    backup_limit,
+                    apply=self.path.endswith("/apply"),
+                )
+        except (
+            KeyError,
+            TypeError,
+            OSError,
+            json.JSONDecodeError,
+            ValueError,
+        ) as error:
             self._json_response(400, {"error": str(error)})
             return
         self._json_response(200, result)

serato_doctor/webui/app.js

@@ -8,7 +8,17 @@ const drilldownTitle = document.querySelector('#drilldown-title');
 const drilldownCount = document.querySelector('#drilldown-count');
 const drilldownSummary = document.querySelector('#drilldown-summary');
 const drilldownList = document.querySelector('#drilldown-list');
+const repairPanel = document.querySelector('#duplicate-repair');
+const repairChoice = document.querySelector('#repair-choice');
+const repairPreview = document.querySelector('#repair-preview');
+const repairMessage = document.querySelector('#repair-message');
+const previewRepairButton = document.querySelector('#preview-repair');
+const applyRepairButton = document.querySelector('#apply-repair');
+const restoreRepairButton = document.querySelector('#restore-repair');
 let latestAnalysis = null;
+let selectedDuplicateGroup = null;
+let previewedRepair = null;
+let latestBackup = null;
 
 function expandHome(path) {
   return path.trim();
@@ -51,19 +61,91 @@ function renderDetail(key) {
   drilldownCount.textContent = `${detail.total ?? 0} found`;
   drilldownSummary.textContent = detail.summary;
 
+  repairPanel.hidden = true;
+  selectedDuplicateGroup = null;
+  previewedRepair = null;
+  latestBackup = null;
+  restoreRepairButton.hidden = true;
   if (!detail.items?.length) {
     drilldownList.innerHTML = '<div class="empty-detail">Nothing to review here. Tiny victory parade, very tasteful.</div>';
     return;
   }
 
-  drilldownList.innerHTML = detail.items.map((item) => `
-    <article class="detail-item">
+  drilldownList.innerHTML = detail.items.map((item, index) => `
+    <article class="detail-item${item.files ? ' selectable-duplicate' : ''}" ${item.files ? `data-duplicate-index="${index}" role="button" tabindex="0"` : ''}>
       <strong>${escapeHtml(item.filename || item.path || 'Untitled item')}</strong>
       <ul>${detailLines(item)}</ul>
+      ${item.files ? '<small>Choose this group to review a safe cleanup →</small>' : ''}
     </article>
   `).join('');
 }
 
+function chooseDuplicate(detailKey, index) {
+  const group = latestAnalysis?.details?.[detailKey]?.items?.[index];
+  if (!group?.files) return;
+  selectedDuplicateGroup = group;
+  previewedRepair = null;
+  applyRepairButton.disabled = true;
+  repairPreview.hidden = true;
+  repairMessage.textContent = '';
+  repairChoice.innerHTML = group.files.map((file, fileIndex) => `
+    <label class="keeper-option"><input type="radio" name="keeper" value="${escapeHtml(file)}" ${fileIndex === 0 ? 'checked' : ''}><span><strong>${fileIndex === 0 ? 'Keep this file' : 'Keep instead'}</strong><small>${escapeHtml(file)}</small></span></label>
+  `).join('');
+  repairPanel.hidden = false;
+  repairPanel.scrollIntoView({behavior: 'smooth', block: 'start'});
+}
+
+function repairPayload() {
+  const keeper = document.querySelector('input[name="keeper"]:checked')?.value;
+  if (!selectedDuplicateGroup || !keeper) throw new Error('Choose a file to keep');
+  return {serato: expandHome(document.querySelector('#serato-path').value), music: expandHome(document.querySelector('#music-path').value), keeper, group_files: selectedDuplicateGroup.files, backup_limit: document.querySelector('#keep-all-backups').checked ? null : Number(document.querySelector('#backup-limit').value)};
+}
+
+async function requestRepair(endpoint) {
+  const response = await fetch(endpoint, {method: 'POST', headers: {'Content-Type': 'application/json'}, body: JSON.stringify(repairPayload())});
+  const data = await response.json();
+  if (!response.ok) throw new Error(data.error || 'Duplicate cleanup failed');
+  return data;
+}
+
+previewRepairButton.addEventListener('click', async () => {
+  repairMessage.textContent = 'Checking the plan…'; applyRepairButton.disabled = true;
+  try {
+    previewedRepair = await requestRepair('/api/duplicates/preview');
+    repairPreview.innerHTML = `<strong>Ready to protect and consolidate</strong><p>${previewedRepair.replaced.length} duplicate file(s) will be backed up, then replaced with shortcuts to the keeper. ${previewedRepair.metadata_backups} Serato metadata file(s) will also be copied into the rollback snapshot. Database V2 will not be changed.</p>`;
+    repairPreview.hidden = false; applyRepairButton.disabled = false;
+    repairMessage.textContent = 'Preview complete. Nothing has changed yet.';
+  } catch (error) { repairMessage.textContent = error.message; }
+});
+
+applyRepairButton.addEventListener('click', async () => {
+  if (!previewedRepair) return;
+  applyRepairButton.disabled = true; repairMessage.textContent = 'Creating the backup before making changes…';
+  try {
+    const result = await requestRepair('/api/duplicates/apply');
+    latestBackup = result.backup;
+    repairMessage.textContent = `Cleanup complete. Restore backup: ${result.backup}`;
+    previewRepairButton.disabled = true;
+    restoreRepairButton.hidden = false;
+  } catch (error) { repairMessage.textContent = error.message; applyRepairButton.disabled = false; }
+});
+
+restoreRepairButton.addEventListener('click', async () => {
+  if (!latestBackup) return;
+  restoreRepairButton.disabled = true; repairMessage.textContent = 'Restoring the duplicate files…';
+  try {
+    const response = await fetch('/api/backups/restore', {method: 'POST', headers: {'Content-Type': 'application/json'}, body: JSON.stringify({serato: expandHome(document.querySelector('#serato-path').value), backup: latestBackup})});
+    const result = await response.json();
+    if (!response.ok) throw new Error(result.error || 'Restore failed');
+    repairMessage.textContent = `Restore complete. ${result.restored.length} original file(s) returned.`;
+    restoreRepairButton.hidden = true;
+  } catch (error) { repairMessage.textContent = error.message; restoreRepairButton.disabled = false; }
+});
+
+repairChoice.addEventListener('change', () => { previewedRepair = null; applyRepairButton.disabled = true; repairPreview.hidden = true; repairMessage.textContent = 'Keeper changed. Preview the plan again.'; });
+drilldownList.addEventListener('click', (event) => { const item = event.target.closest('[data-duplicate-index]'); if (item) chooseDuplicate(document.querySelector('.drill-trigger.selected')?.dataset.detail, Number(item.dataset.duplicateIndex)); });
+drilldownList.addEventListener('keydown', (event) => { if (event.key !== 'Enter' && event.key !== ' ') return; const item = event.target.closest('[data-duplicate-index]'); if (item) { event.preventDefault(); chooseDuplicate(document.querySelector('.drill-trigger.selected')?.dataset.detail, Number(item.dataset.duplicateIndex)); } });
+
 function render(data) {
   latestAnalysis = data;
   document.querySelectorAll('[data-field]').forEach((element) => {

serato_doctor/webui/index.html

@@ -23,7 +23,7 @@
       </nav>
       <div class="safety-card">
         <span class="safety-icon">✓</span>
-        <div><strong>Read-only mode</strong><p>Your library will not be modified.</p></div>
+        <div><strong>Protected mode</strong><p>Analysis is read-only. Repairs require a preview and backup.</p></div>
       </div>
       <div class="sidebar-foot">Local interface · v0.1</div>
     </aside>
@@ -88,6 +88,23 @@
           <p id="drilldown-summary">Click a metric above to see example files and saved paths behind that number.</p>
           <div id="drilldown-list" class="detail-list"></div>
         </div>
+
+        <div id="duplicate-repair" class="repair-panel panel" hidden>
+          <div class="section-heading"><div><p class="eyebrow">Backup-first cleanup</p><h2>Safely consolidate duplicates</h2></div><span class="repair-tag">Preview required</span></div>
+          <p>Choose the real file to keep. Every other path will be backed up and replaced with a shortcut to it, so existing Serato crates remain mapped. Serato’s database V2 is never edited.</p>
+          <div id="repair-choice" class="repair-choice"></div>
+          <div class="backup-options">
+            <label>Backups to keep <input id="backup-limit" type="number" min="1" value="10"></label>
+            <label class="check-label"><input id="keep-all-backups" type="checkbox"> Keep every backup</label>
+          </div>
+          <div id="repair-preview" class="repair-preview" hidden></div>
+          <div class="repair-actions">
+            <button id="preview-repair" type="button">Preview changes</button>
+            <button id="apply-repair" class="danger-action" type="button" disabled>Apply backed-up cleanup</button>
+            <button id="restore-repair" type="button" hidden>Restore this backup</button>
+          </div>
+          <div id="repair-message" class="repair-message" role="status"></div>
+        </div>
       </section>
     </main>
   </div>

tests/test_repair.py

@@ -0,0 +1,67 @@
+from pathlib import Path
+
+import pytest
+
+from serato_doctor.repair import (
+    BACKUP_FOLDER,
+    apply_duplicate_repair,
+    plan_duplicate_repair,
+    restore_backup,
+    rotate_backups,
+)
+
+
+def library(tmp_path):
+    serato = tmp_path / "_Serato_"
+    crate = serato / "Subcrates" / "House.crate"
+    crate.parent.mkdir(parents=True)
+    crate.write_bytes(b"crate-data")
+    (serato / "database V2").write_bytes(b"database-data")
+    music = tmp_path / "Music"
+    keeper = music / "Main" / "Track.mp3"
+    duplicate = music / "Old" / "Track.mp3"
+    keeper.parent.mkdir(parents=True)
+    duplicate.parent.mkdir(parents=True)
+    keeper.write_bytes(b"keeper")
+    duplicate.write_bytes(b"duplicate")
+    return serato, keeper, duplicate
+
+
+def test_duplicate_repair_backs_up_then_preserves_old_path_as_link(tmp_path):
+    serato, keeper, duplicate = library(tmp_path)
+    plan = plan_duplicate_repair(keeper, (keeper, duplicate), serato)
+
+    receipt = apply_duplicate_repair(plan, serato, backup_limit=3)
+
+    assert duplicate.is_symlink()
+    assert duplicate.resolve() == keeper.resolve()
+    assert (receipt.backup / "manifest.json").is_file()
+    assert any((receipt.backup / "serato-metadata").rglob("House.crate"))
+    assert any((receipt.backup / "serato-metadata").rglob("database V2"))
+
+    restored = restore_backup(receipt.backup)
+    assert restored == (duplicate.resolve(),)
+    assert not duplicate.is_symlink()
+    assert duplicate.read_bytes() == b"duplicate"
+
+
+def test_plan_rejects_keeper_outside_duplicate_group(tmp_path):
+    serato, keeper, duplicate = library(tmp_path)
+    outsider = tmp_path / "outsider.mp3"
+    outsider.write_bytes(b"other")
+
+    with pytest.raises(ValueError, match="must belong"):
+        plan_duplicate_repair(outsider, (keeper, duplicate), serato)
+
+
+def test_backup_rotation_can_be_limited_or_unlimited(tmp_path):
+    root = tmp_path / BACKUP_FOLDER
+    for name in ("001", "002", "003"):
+        backup = root / name
+        backup.mkdir(parents=True)
+        (backup / "manifest.json").write_text("{}", encoding="utf-8")
+
+    rotate_backups(root, None)
+    assert len(list(root.iterdir())) == 3
+    rotate_backups(root, 2)
+    assert {path.name for path in root.iterdir()} == {"002", "003"}

tests/test_web.py

@@ -3,7 +3,7 @@ from pathlib import Path
 
 import pytest
 
-from serato_doctor.web import STATIC_FILES, analyze_paths
+from serato_doctor.web import STATIC_FILES, analyze_paths, duplicate_repair
 
 
 def test_web_analysis_uses_production_health_pipeline(tmp_path):
@@ -49,3 +49,24 @@ def test_web_static_assets_are_declared_and_packaged():
     assert 'data-detail="database_missing_tracks"' in html
     assert 'data-detail="old_crate_references"' in html
     assert html.count('class="info-button"') >= 10
+
+
+def test_duplicate_repair_preview_does_not_change_files(tmp_path):
+    serato = tmp_path / "_Serato_"
+    serato.mkdir()
+    music = tmp_path / "Music"
+    first = music / "A" / "Track.mp3"
+    second = music / "B" / "Track.mp3"
+    first.parent.mkdir(parents=True)
+    second.parent.mkdir(parents=True)
+    first.write_bytes(b"first")
+    second.write_bytes(b"second")
+
+    result = duplicate_repair(
+        serato, music, first, (first, second), backup_limit=10
+    )
+
+    assert result["applied"] is False
+    assert result["database_v2_modified"] is False
+    assert second.read_bytes() == b"second"
+    assert not second.is_symlink()