Add backward compatibility for detached worktrees

Detached worktrees created before this fix (or via raw git commands)
don't have stored names in config. Added path-based inference to handle
these cases.

Changes:
- Added _infer_name_from_path() method to infer names from worktree paths
- Fallback chain: stored config → inferred from path → (detached-<commit>)
- Works with common path patterns like ../{repo}-{name} and ../{name}
- Added test for backward compatibility scenario

This ensures switch/list/run commands work even for legacy detached worktrees.

Author: claude

tools/wt-worktree/notes.md

@@ -169,6 +169,8 @@ wt-worktree/
    - Key Insight: Git's `--worktree` config flag requires `extensions.worktreeConfig` to be enabled first
    - Tests: Added 6 comprehensive tests for detached worktree creation, listing, switching, running commands, and deletion
    - Lesson: Per-worktree config in git requires enabling the worktreeConfig extension, and is the right way to store worktree-specific metadata
+   - Backward Compatibility: Added `_infer_name_from_path()` to infer names from path patterns for detached worktrees created before this fix or via raw git commands
+   - Fallback chain: stored config → inferred from path → `(detached-<commit>)`
 
 ### Future Improvements
 

tools/wt-worktree/tests/test_cli.py

@@ -404,3 +404,34 @@ def test_detached_worktree_delete(runner, initialized_repo, no_prompt):
     manager = WorktreeManager(config)
     wt = manager.find_worktree_by_name("mydetached")
     assert wt is None
+
+
+def test_detached_worktree_backward_compatibility(runner, initialized_repo, no_prompt):
+    """Test that detached worktrees created without stored name still work."""
+    # Create a detached worktree using raw git (simulates old behavior)
+    from wt import git
+    from wt.config import Config
+    from wt.worktree import WorktreeManager
+
+    config = Config(initialized_repo)
+    wt_path = config.resolve_path_pattern("legacy", "feature/legacy")
+    git.add_worktree(wt_path, "legacy", create_branch=False, base="HEAD",
+                     detached=True, repo_path=initialized_repo)
+
+    # Note: Not calling set_worktree_name - simulates old behavior
+
+    # List should infer name from path
+    manager = WorktreeManager(config)
+    worktrees = manager.list_worktrees()
+    legacy_wt = None
+    for wt in worktrees:
+        if "legacy" in wt["name"]:
+            legacy_wt = wt
+            break
+
+    assert legacy_wt is not None
+    assert legacy_wt["name"] == "legacy"  # Inferred from path
+
+    # Should be able to find it by inferred name
+    found_wt = manager.find_worktree_by_name("legacy")
+    assert found_wt is not None

tools/wt-worktree/wt/worktree.py

@@ -20,6 +20,37 @@ def __init__(self, config: Config):
         self.config = config
         self.repo_root = config.repo_root
 
+    def _infer_name_from_path(self, wt_path: Path) -> Optional[str]:
+        """
+        Try to infer worktree name from its path based on path_pattern.
+
+        Provides backward compatibility for detached worktrees created before
+        the name-storing feature was added.
+
+        Args:
+            wt_path: Path to the worktree
+
+        Returns:
+            Inferred name or None
+        """
+        # Get the pattern and try common formats
+        pattern = self.config.get("path_pattern")
+        repo_name = self.repo_root.name
+
+        # Try pattern: ../{repo}-{name}
+        if pattern == "../{repo}-{name}":
+            expected_prefix = f"{repo_name}-"
+            if wt_path.name.startswith(expected_prefix):
+                return wt_path.name[len(expected_prefix):]
+
+        # Try pattern: ../{name}
+        elif pattern == "../{name}":
+            # Exclude the main worktree
+            if wt_path != self.repo_root:
+                return wt_path.name
+
+        return None
+
     def list_worktrees(self) -> List[dict]:
         """
         List all worktrees with enhanced information.
@@ -40,13 +71,18 @@ def list_worktrees(self) -> List[dict]:
             if wt.get("branch"):
                 wt["name"] = self.config.extract_worktree_name(wt["branch"])
             else:
-                # For detached worktrees, try to get name from git config
+                # For detached worktrees, try multiple sources
                 stored_name = git.get_worktree_name(wt["path"])
                 if stored_name:
                     wt["name"] = stored_name
                 else:
-                    # Fallback: use commit hash as identifier
-                    wt["name"] = f"(detached-{wt['commit'][:7]})"
+                    # Try to infer from path (backward compatibility)
+                    inferred_name = self._infer_name_from_path(wt["path"])
+                    if inferred_name:
+                        wt["name"] = inferred_name
+                    else:
+                        # Fallback: use commit hash as identifier
+                        wt["name"] = f"(detached-{wt['commit'][:7]})"
 
         return worktrees