detect_changes: impacted_symbols always empty for projects inside git worktrees (canonical_root miscalculated) #659

Summary

detect_changes correctly returns changed_files but always returns impacted_symbols: [] / impacted_count: 0 when the indexed project lives inside a git worktree (not the worktree root itself).

The root cause is that canonical_root is computed one level too high, causing a path prefix mismatch between git diff output and graph file paths.

Environment

• codebase-memory-mcp: v0.8.1
• OS: macOS 25.5.0 (Darwin)
• Project layout: git monorepo at /workspace/, with sub-projects indexed from subdirectories (e.g., /workspace/scripts/, /workspace/runtime/solar-monitor/)

Repository Structure

/workspace/                         ← actual git root (.git lives here)
├── scripts/
│   └── solar_daily_report_v1.py   ← indexed as project "workspace-scripts"
├── runtime/
│   └── solar-monitor/              ← indexed as project "workspace-runtime-solar-monitor"

Steps to Reproduce

1. Index a project whose root_path is a subdirectory of the git worktree root (e.g., workspace/scripts/)
2. Call detect_changes with scope: "impact" and since: "HEAD~1"

{
  "project": "Users-openclaw-.openclaw-workspace-scripts",
  "since": "HEAD~1",
  "scope": "impact",
  "depth": 2
}

3. Observe: changed_files is correctly populated; impacted_symbols is []

Expected Behavior

impacted_symbols should list all symbols in the changed files plus their transitive callers.

Actual Behavior

{
  "changed_files": ["scripts/solar_daily_report_v1.py", ...],
  "changed_count": 120,
  "impacted_symbols": [],
  "impacted_count": 0,
  "depth": 2
}

Root Cause

list_projects reveals the miscalculation:

{
  "name": "Users-openclaw-.openclaw-workspace-scripts",
  "root_path": "/Users/openclaw/.openclaw/workspace/scripts",
  "git": {
    "worktree_root": "/Users/openclaw/.openclaw/workspace",
    "git_common_dir": "../.git",
    "canonical_root": "/Users/openclaw/.openclaw/workspace/.."
  }
}

The path prefix that detect_changes strips from git diff paths (workspace/scripts/) does not match what the graph stored (solar_daily_report_v1.py relative to root_path), so no symbols are ever matched.

The symbol is present in the graph (verified via search_graph):

{
  "name": "solar_daily_report_v1.py",
  "qualified_name": "Users-openclaw-.openclaw-workspace-scripts.solar_daily_report_v1",
  "label": "Module",
  "file_path": "solar_daily_report_v1.py",
  "out_degree": 81
}

The canonical_root appears to be computed as worktree_root + "/" + git_common_dir + "/.." which for git_common_dir = "../.git" resolves to workspace/../.git/.. = .openclaw/ instead of the correct workspace/.

Workaround

Currently falling back to manual trace_path + search_graph to assess blast radius for shared library changes.

Additional Notes

• changed_files detection works correctly in all cases
• Projects indexed from the worktree root directly are unaffected
• Standalone git repos (not worktrees) are unaffected — detect_changes works correctly there
• This affects all Users-openclaw-.openclaw-workspace-* projects (anything inside the workspace)