Diff Project

---
name: diff-project
description: Shows what changed in dotforge since the project's last sync, to decide whether running /forge sync is worthwhile.
---

# Diff Project

Show what changed in dotforge since the last synchronization of the current project.

## Step 1: Identify project baseline

1. Read `$DOTFORGE_DIR/registry/projects.yml`
2. Find the current project by `path` (compare with `$PWD`)
3. Get `dotforge_version` and `last_sync`
4. If no `dotforge_version` is registered (null), report:
   ```
   Project not synced — no baseline to compare against.
   Run /forge sync to establish baseline.
   ```
   And stop.

## Step 2: Verify local manifest

If `.claude/.forge-manifest.json` exists in the current project:
1. Read it and get the version and file hashes
2. For each file in the manifest, calculate `shasum -a 256 <file> | cut -d' ' -f1`
3. Compare against the registered hash
4. Report locally modified files (hash differs) and deleted files
5. Use the manifest version as baseline (more precise than the registry)

If manifest does NOT exist, continue to Step 3 using git log.

## Step 3: Detect changes in dotforge

Run in `$DOTFORGE_DIR/`:

```bash
git log --oneline v<version>..HEAD -- template/ stacks/
```

Where `<version>` is the tag corresponding to the project's `dotforge_version`.

If the tag does not exist, use `last_sync` as reference:
```bash
git log --oneline --since="<last_sync>" -- template/ stacks/
```

If there are no relevant commits, report:
```
dotforge has no changes in template/stacks since v<version>.
Project is up to date.
```

## Step 4: Show change summary

For each modified file in template/ or relevant stacks/ for the project:

```
═══ DIFF dotforge: v<previous> → v<current> ═══
Project: <name> (last sync: <date>)

Files modified in dotforge:
  template/hooks/block-destructive.sh — <diff summary>
  template/rules/_common.md — <diff summary>
  stacks/python-fastapi/rules/backend.md — <diff summary>

Local files with modifications (vs manifest):
  .claude/rules/_common.md — hash differs from deployed
```

Filter stacks/ to show only the stacks used by the project (read from registry).

## Step 5: Recommend action

If there are relevant changes:
```
Recommendation: run /forge sync to incorporate these changes.
```

If there are only cosmetic changes or changes in unused stacks:
```
Changes do not affect this project. Sync is not necessary.
```

## Installation

This skill is installed automatically if the `skills/` symlink already exists in `~/.claude/skills/`. If not, create the symlink:
```bash
ln -sf $DOTFORGE_DIR/skills ~/.claude/skills
```