Analyze Knowledge

Analyze git history to surface code expertise, suggest reviewers, and assess knowledge concentration risk.

1. Determine Mode and Scope

Auto-detect from user intent:

Mode	Triggers	Default scope
Reviewer	"who should review", "find reviewers", "suggest reviewers"	Changed files: git diff --name-only $(git merge-base HEAD main)..HEAD
Distribution	"who knows", "lottery factor", "bus factor", "knowledge spread", "expertise"	User-specified directory, or repo root

If scope is ambiguous, ask. Accept:

• Explicit paths or globs
• A PR number (extract changed files via gh pr diff --name-only)
• A directory
• "whole repo" (default for distribution mode)

Exclude generated files: check for // Code generated or DO NOT EDIT headers.

2. Normalize Authors

# Check for .mailmap
if [ -f .mailmap ]; then
  MAILMAP_FLAG="--use-mailmap"
else
  MAILMAP_FLAG=""
fi

• Pass $MAILMAP_FLAG to all git commands.
• If no .mailmap, group by author name (not email) to merge multiple addresses.
• Filter bots: exclude authors matching [bot], dependabot, renovate, github-actions, or emails containing noreply@github.com with non-human names.

2.5. Fan out for broad scope

When scope is large, delegate per-area data collection to subagents so main context never sees raw blame/log output for hundreds of files. Aligns with parallelize-subagents (delegate when output would flood main context) and delegate-investigation (read-only history work belongs in Explore).

Trigger	Strategy
Distribution mode, "whole repo" or >20 directories in scope	One Explore subagent per top-level directory; each runs its tiered collection and returns the per-area summary only.
Reviewer mode, >20 changed files	Batch files in groups of ~10; one Explore subagent per batch returning per-file expert lists.
Tier 3 line-level on >5 files	One Explore subagent per file (blame output is voluminous).
Anything smaller	Run inline. Don't spin up a subagent for one git shortlog.

Each subagent prompt follows subagent-prompt-contract:

• Goal: "Return top-N authors per file in <area>, with weighted contribution scores"
• Inline context: paths, $MAILMAP_FLAG state, the recency weighting table from step 4, the git command(s) to run
• Output shape: Markdown table only, ≤30 lines
• Constraints: read-only (Explore enforces this); do not spawn further subagents
• Model: haiku (per subagent-model-routing) — mechanical aggregation; output is bounded and requires no architectural reasoning
• Return: prefix the summary with Status: DONE | DONE_WITH_CONCERNS | BLOCKED | NEEDS_CONTEXT

Parent merges per-area returns into the final table in step 5.

3. Collect Data (Tiered)

Tier 1: Commit counts (always run, fast)

git shortlog -sne --no-merges $MAILMAP_FLAG -- <paths> | head -20

Use this for a quick overview. Sufficient when the user just wants a rough sense.

Tier 2: File-level changes (default)

git log --no-merges --since="2 years ago" $MAILMAP_FLAG \
  --format='COMMIT:%H|%an|%aI' --numstat -- <paths>

Parse with jq pipelines from reference.md. This produces per-author, per-file change counts with timestamps for recency weighting.

For large repos or broad scope, add --since="1 year ago" to keep it fast.

Tier 3: Line-level blame (opt-in, small file sets only)

Only use when:

• User explicitly asks for deep/line-level analysis
• Scope is ≤15 files

git blame --porcelain $MAILMAP_FLAG <file> | \
  awk '/^author /{print}' | sort | uniq -c | sort -rn

For >5 files, fan out per step 2.5 (one Explore subagent per file). For ≤5 files, parallelize inline with xargs -P4.

4. Analyze

Recency Weighting

Weight contributions by age:

Age	Weight
< 6 months	1.0
6–12 months	0.7
12–24 months	0.4
> 24 months	0.1

Reviewer Mode

1. For each file in scope, compute weighted contribution score per author
2. Aggregate across all files: an author touching many of the changed files scores higher
3. Exclude the PR author (current git config user.name) from suggestions
4. Rank by score, present top 3–5
5. For each reviewer, list the directories/files where they have the most expertise

Distribution Mode

1. Group files by directory (auto-detect depth: <20 files → no grouping, 20–200 → 1 level, 200+ → 2 levels)
2. Per area, compute:
   • Top experts: authors ranked by weighted contribution
   • Lottery factor: count of authors contributing ≥10% of weighted changes
   • Concentration: percentage of changes from the top contributor
3. Flag risk levels:
   • HIGH: lottery factor = 1 (single expert)
   • MEDIUM: lottery factor = 2
   • LOW: lottery factor ≥ 3

5. Present Results

Output directly to terminal. No file output.

Reviewer Mode

## Suggested Reviewers (<N> files from <source>)

| Rank | Reviewer       | Score | Key areas                   | Last active  |
|------|----------------|-------|-----------------------------|--------------|
| 1    | Alice Smith    | 0.82  | internal/auth/, pkg/tokens/ | 2 weeks ago  |
| 2    | Bob Jones      | 0.65  | internal/auth/              | 1 month ago  |
| 3    | Carol Lee      | 0.41  | pkg/tokens/, cmd/server/    | 3 months ago |

Distribution Mode

## Knowledge Distribution: <scope>

| Area                 | Top experts                       | Lottery factor | Risk   |
|----------------------|-----------------------------------|----------------|--------|
| internal/auth/oauth/ | Alice (0.9)                       | 1              | HIGH   |
| internal/auth/jwt/   | Alice (0.6), Bob (0.5)            | 2              | MEDIUM |
| internal/auth/rbac/  | Bob (0.4), Carol (0.3), Dan (0.3) | 3              | LOW    |

### Concentration Warnings

- **internal/auth/oauth/**: single expert; Alice authored 94% of recent changes
- **internal/auth/jwt/**: two experts with significant overlap

Edge Cases

• Squash-imported repo: if total unique authors < 3 or median commits/author < 2, warn that history may not be representative
• Monorepo with many contributors: use tier 2 scoped to paths + time window; never run tier 3 on broad scope
• No changes in scope (reviewer mode): fall back to directory-level analysis of the files' parent directories

Guidelines

• Use jq for all JSON/pipeline processing (see reference.md for templates)
• Present findings conversationally: tables for data, plain text for warnings and recommendations
• When suggesting reviewers, mention why each person is suggested (which files/areas they know)
• For distribution analysis, lead with the highest-risk areas
• Per ~/.claude/rules/probe-not-assume.md: confirm via tool/command before recommending; do not infer.