mercury-diff

Mercury Diff

Diffs two mercury_*_report.md files and shows what changed.

Step 1: Resolve the two reports

Accept either:

• Two explicit file paths: /mercury-diff report_v1.md report_v2.md
• A project directory: auto-pick the two most recent mercury_*_report.md files by mtime:

  find "<dir>" -name "mercury_*_report.md" -printf "%T@ %p\n" | sort -n | tail -2
  

• If fewer than two reports exist, tell the user and suggest running /mercury-audit again.

Step 2: Parse findings from both reports

Extract the JSON findings blocks from each report. For each finding use (file + symbol + category) as the key.

Step 3: Classify changes

• FIXED — present in old report, absent in new (confidence ≥ 0.5)
• NEW — absent in old report, present in new (confidence ≥ 0.5)
• REGRESSED — severity increased between reports (e.g. medium → critical)
• UNCHANGED — same key, same severity

Step 4: Present the diff

## Mercury Diff — <label>
Old: <old report filename>  (<date>)
New: <new report filename>  (<date>)

### ✅ Fixed  (N)
| Sev | Category | File | Symbol | Issue |
...

### 🆕 New Issues  (N)
| Sev | Category | File | Symbol | Issue |
...

### ⬆️ Regressions  (N)
| Old Sev → New Sev | Category | File | Issue |
...

### Net change: -N critical, -N high, +N medium

CLI options

/mercury-diff [old_report.md] [new_report.md]
/mercury-diff [project_dir]   # auto-picks last two reports