diff-intake

What this skill does

# diff-intake

Follow this skill step by step.
You are step 1 of the analytics instrumentation workflow. Produce a compact
YAML change brief that downstream skills (discover-event-surfaces,
instrument-events) will consume. Keep the output machine-readable and
precise — no prose around the YAML block.

## Step 1: Gather changed files and categorize

Fetch the list of changed files from the source, then categorize each one.

### Fetching changes
- **PR URL**
`gh pr view <number-or-url>`
`gh pr view <pr-number> --json files --jq '.files[] | "\(.path)\t+\(.additions) -\(.deletions)\t"'`
- **Branch comparison**
`git log <main|master>..<branch>`
`git diff --stat <main|master>..<branch>`
- **Ambiguous mention** (PR number, branch name): infer the right form and fetch without asking unless auth fails.

### Categorize files
Assign each file to a category based on its path:
- **Core Logic**: application source (e.g. src/auth/login.py, database/models.ts)
- **Generated**: anything with `generated` in its path
- **Testing**: test files
- **Config / Dependencies**: package.json, docker-compose.yml, etc.
- **Documentation**: READMEs, docs/
- **Noise**: lock-files, .svg, auto-generated migrations

For each file, record: path, category, change type (Added / Modified / Deleted), and analytics likelihood (1–5).

## Step 2: Build the file summary map
Read every single **Core Logic** file and create the file summary map.
Only process and include **Core Logic** files.

### Fetching detailed diffs
- **PR**
`gh pr view <number-or-url> --json baseRefOid,headRefOid`
Using the response, get a detailed diff
`git diff <baseRefOid>...<headRefOid> -- <file1> <file2> <file_n>`
- **Branch comparison**
`git diff main..feature/foo  -- <file1> <file2> <file_n>`

### For each file, record
- `summary` — 2-line summary of what changed
- `stack` — frontend, backend, or shared

### Also derive user-facing changes and touched surfaces

While reading the diff and the changed files, also produce the higher-level
signals that downstream event discovery needs:

- `user_facing_changes` — a flat list of concrete behavior changes that matter
  to a user, PM, or analyst. Each item should describe what a user can now do,
  see, or experience differently. Omit purely internal refactors.
- `surfaces.components` — the UI components, routes, pages, handlers, or other
  interaction surfaces directly involved in those user-facing changes. Prefer
  likely instrumentation points over low-level helpers.

For each surface, record:
- `name` — component, route, page, hook, or surface name
- `file` — repo-relative path
- `change` — `added`, `modified`, or `deleted`

If the change is backend-only or has no clear interactive surface, omit
`surfaces.components` rather than inventing one.

## Step 3: Classify the overall change

Infer the change type and analytics scope:

| Type                                     | Analytics implication                             |
| ---------------------------------------- | ------------------------------------------------- |
| feat                                     | High — new surfaces likely need tracking          |
| fix                                      | Low–Medium — may affect existing event conditions |
| refactor                                 | Low — tracking paths may move, regression risk    |
| perf                                     | Low — usually no tracking impact                  |
| revert                                   | Medium — need to check what tracking was lost     |
| style / docs / test / build / ci / chore | None — skip analytics analysis                    |

`analytics_scope` = highest implication present:
- `none` — only no-impact types
- `low` — only perf/refactor
- `medium` — fix
- `high` — any feature or capability addition

If `analytics_scope` is `none`, emit the brief and note that downstream skills are not needed.

## Step 4: Emit the YAML brief
Output only the YAML block — no prose before or after. Follow the format exactly.
List each file individually in file_summary_map (no globs).

```yaml
change_brief:
  classification:
    primary: feat           # dominant conventional commit type
    types: [feat, fix]      # all types detected
    analytics_scope: high   # none | low | medium | high
    stack: frontend         # frontend | backend | fullstack
  summary: "One sentence describing the overall change"
  user_facing_changes:
    - "Users can now upload an avatar with drag-and-drop and preview it before saving."
  surfaces:
    components:
      - name: "AvatarUpload"
        file: "src/components/AvatarUpload.tsx"
        change: modified
  file_summary_map:         # each entry includes a layer field
    - file: "src/components/AvatarUpload.tsx"
      summary: "New component for avatar upload with drag-and-drop and preview"
      layer: frontend       # frontend | backend | shared
    - file: "src/api/upload.ts"
      summary: "Upload endpoint handler, validates file type and persists to S3"
      layer: backend
```