Stage 2 Research

---
name: talk-stage2-research
description: "Performs git archaeology, changelog analysis, and builds a verified factual timeline by cross-referencing git history with source material. REX mode only (skipped automatically in Concept mode). Use when building a REX talk and you need verified commit metrics, release timelines, and contributor data from a git repository."
allowed-tools: Write Read Bash
effort: low
---

# Talk Stage 2: Research (REX mode only)

Builds the git proof for a REX talk. Cross-references git history, CHANGELOG, and the Stage 1 summary to produce a verified timeline and velocity analysis.

**Automatically skipped in `--concept` mode.** Only runs when the source material is a REX with git repository access.

## When to use this skill

- After Stage 1 (Extract) when building a REX talk
- When you have access to the project's git repository
- To verify metrics mentioned in the source material against actual git data

## What this skill does

1. **Reads the summary**: understands the period and themes from Stage 1
2. **Git archaeology**: extracts velocity metrics (read-only commands only)
3. **Changelog analysis**: scans releases, features, documented metrics
4. **Cross-references**: aligns git, CHANGELOG, and summary
5. **Builds the timeline**: verified dates, not estimated
6. **Writes 3 output files**

## Input

- `talks/{YYYY}-{slug}-summary.md` (from Stage 1, required)
- `repo_path`: absolute path to the git repository
- Optional: CHANGELOG path if different from `{repo_path}/CHANGELOG.md`

## Output

Three files:
- `talks/{YYYY}-{slug}-git-archaeology.md`
- `talks/{YYYY}-{slug}-changelog-analysis.md`
- `talks/{YYYY}-{slug}-timeline.md`

## Git Commands (read-only only)

```bash
# Commits by month
git -C {repo_path} log --pretty=format:"%Y-%m" | sort | uniq -c

# Commits by contributor
git -C {repo_path} shortlog -sn --no-merges

# First and last date
git -C {repo_path} log --pretty=format:"%ad" --date=short | tail -1
git -C {repo_path} log --pretty=format:"%ad" --date=short | head -1

# Merged PRs (if merge commit convention)
git -C {repo_path} log --merges --oneline | wc -l

# Tags (releases)
git -C {repo_path} tag --sort=version:refname

# Velocity peak (busiest months)
git -C {repo_path} log --pretty=format:"%Y-%m" | sort | uniq -c | sort -rn | head -5
```

## Output formats

### git-archaeology.md

```markdown
# Git Archaeology: {slug}

**Repo**: {repo_path}
**Period analyzed**: {start date} -> {end date}
**Commands run**: {list}

## Global Metrics

| Metric | Value | Source |
|--------|-------|--------|
| Total commits | {n} | git log |
| Total merges/PRs | ~{n} | git log --merges |
| Total releases (tags) | {n} | git tag |
| Human contributors | {n} | git shortlog |
| Period covered | {n} months | first -> last date |

## Monthly Velocity

| Month | Commits | Notes |
|-------|---------|-------|
| {YYYY-MM} | {n} | {context if notable} |
...

## Contributors

| Rank | Name | Commits | % |
|------|------|---------|---|
| 1 | {name} | {n} | {%} |
...

---
*Generated by talk-stage2-research: {date}*
```

### changelog-analysis.md

```markdown
# Changelog Analysis: {slug}

**Source**: {CHANGELOG path}
**Releases analyzed**: {n} (v{first} -> v{last})

## Features by release (summary)

| Release | Date | Key features | Metrics mentioned |
|---------|------|--------------|------------------|
| {version} | {date} | {features} | {metrics} |
...

## Patterns identified

### Acceleration
{Periods of high velocity and what drove them}

### Inflection points
{Direction changes, major releases}

### Verifiable metrics in CHANGELOG
{Exhaustive list of numbers mentioned in CHANGELOG with their release}

---
*Generated by talk-stage2-research: {date}*
```

### timeline.md

```markdown
# Factual Timeline: {slug}

**Period**: {start} -> {end} ({n} months)
**Cross-referenced sources**: Summary x Git history x CHANGELOG

---

## Month-by-month timeline

| Month | Commits | Releases | Versions | Key features | Talk event |
|-------|---------|----------|----------|--------------|-----------|
| {YYYY-MM} | {n} | {n} | {versions} | {features} | {anecdote/event} |
...

## Cross-reference: Conflicts and inconsistencies

{If dates or metrics contradict between sources, note here}

---
*Generated by talk-stage2-research: {date}*
*Sources: git log x {CHANGELOG path} x {summary path}*
```

## Key rules

- **Read-only only**: no git commands that modify repo state
- **Verify before asserting**: a date not found in git = "unverified"
- **Cross-reference**: flag inconsistencies between sources, don't pick one arbitrarily
- **Granularity**: month by month minimum; week by week if the period is short (< 2 months)

## Anti-patterns

- Running git commands that modify the repository
- Estimating dates instead of verifying them in git
- Rounding metrics without flagging it
- Silently merging contradictory data from different sources
- Omitting quiet periods (plateaus tell a story too)

## Validation checklist

- [ ] Only read-only git commands executed
- [ ] Timeline covers the full period from summary
- [ ] All metrics have an explicit source (git or CHANGELOG)
- [ ] Conflicts between sources flagged in dedicated section
- [ ] 3 files generated and saved

## Tips

- The timeline is what Stage 3 (Concepts) uses to enrich concept scores; a good timeline makes the concept catalogue stronger
- "Quiet periods" in git velocity often correspond to hardest engineering challenges, worth noting
- If the CHANGELOG has no version tags, fall back to date-based anchoring

## Related

- [Stage 1: Extract](../stage-1-extract/SKILL.md): prerequisite
- [Stage 3: Concepts](../stage-3-concepts/SKILL.md): reads this timeline
- [Orchestrator](../orchestrator/SKILL.md)