historical-pattern-analysis

# Historical Pattern Analysis

## Overview

Analyze git history and memory to learn from past infrastructure changes. Identify patterns, recurring issues, and apply lessons learned to current work.

**Announce at start:** "I'm using the historical-pattern-analysis skill to learn from past changes."

## When to Use

- Before making changes similar to past changes
- When investigating recurring issues
- To understand why infrastructure is configured a certain way
- To identify change patterns and team practices

## Process

### Step 1: Define Search Scope

Determine what history to analyze:
- Specific resources being changed
- Time period (last month, quarter, year)
- Specific team members or patterns

### Step 2: Git Archaeology

#### Find Related Commits

```bash
# Commits touching specific files
git log --oneline -20 -- "path/to/module/*.tf"

# Commits mentioning resource types
git log --oneline -20 --grep="aws_security_group"

# Commits by pattern in message
git log --oneline -20 --grep="fix\|rollback\|revert"

# Commits in date range
git log --oneline --since="2024-01-01" --until="2024-06-01" -- "*.tf"
```

#### Analyze Commit Patterns

```bash
# Most frequently changed files
git log --pretty=format: --name-only -- "*.tf" | sort | uniq -c | sort -rn | head -20

# Authors and their focus areas
git shortlog -sn -- "environments/prod/"

# Change frequency by day/time
git log --format="%ad" --date=format:"%A %H:00" -- "*.tf" | sort | uniq -c
```

#### Find Reverts and Fixes

```bash
# Revert commits
git log --oneline --grep="revert\|Revert"

# Fix commits following changes
git log --oneline --grep="fix\|hotfix\|Fix"

# Commits with "URGENT" or "EMERGENCY"
git log --oneline --grep="urgent\|emergency" -i
```

### Step 3: Analyze Change Patterns

#### Coupling Analysis

Which files change together?
```bash
# For a specific file, what else changes with it?
git log --pretty=format:"%H" -- "modules/vpc/main.tf" | \
  xargs -I {} git show --name-only --pretty=format: {} | \