Project 13: Repository Analytics Dashboard — Mine Git History for Insights
A dashboard that analyzes repository history to show contribution patterns, code hotspots, team dynamics, and technical debt indicators—like a mini version of GitPrime or Pluralsight Flow.
Quick Reference
| Attribute | Value |
|---|---|
| Difficulty | Advanced |
| Time Estimate | 2-3 weeks |
| Main Programming Language | Python |
| Alternative Programming Languages | TypeScript, Go, Rust |
| Coolness Level | Level 4: Hardcore Tech Flex |
| Business Potential | 3. The “Service & Support” Model |
| Prerequisites | Data analysis basics, understanding of Git history |
| Key Topics | Git Log Formats, Software Engineering Metrics, Data Visualization |
1. Learning Objectives
By completing this project, you will:
- Implement a working version of: A dashboard that analyzes repository history to show contribution patterns, code hotspots, team dynamics, and technical debt indicators—like a mini version of GitPrime or Pluralsight Flow..
- Explain the core Git workflow tradeoff this project is designed to surface.
- Design deterministic checks so results can be verified and reproduced.
- Document operational failure modes and safe recovery actions.
2. All Theory Needed (Per-Concept Breakdown)
Git Log Formats
Fundamentals
This concept matters in this project because your implementation will fail or become non-deterministic without a precise model of Git Log Formats. You should define what the concept controls, what invariants must hold, and which actions are safe versus destructive. Treat this concept as a production concern, not a tutorial checkbox.
Deep Dive into the concept
When applying Git Log Formats in this project, reason in three passes: data shape, state transitions, and enforcement. First, identify which artifacts are authoritative (commit objects, refs, metadata, policy config, CI status, or scan findings). Second, map how those artifacts change when your tool runs. Third, define failure behavior explicitly. In Git tooling, silent partial success is dangerous: you need either complete success with evidence or an explicit failure state with remediation guidance. Also account for scale behavior. A workflow that works on a toy repo may fail on large history depth, concurrent updates, or mixed branch policies. Include trace logs for every irreversible action, and separate simulation mode from write mode. For interview readiness, be able to explain how this concept protects delivery speed while reducing operational risk.
How this fit on projects
In this project, Git Log Formats is directly used in design decisions, implementation constraints, and verification criteria.
Definitions & key terms
Git Log Formatsinvariant: A condition that must remain true before and after every operation.- Safety boundary: The point where actions become destructive unless guarded.
- Verification signal: Evidence proving the action behaved as expected.
Mental model diagram
Input state -> Validate invariant -> Apply change -> Verify output -> Record evidence
How it works
- Capture current state and constraints.
- Evaluate whether
Git Log Formatspreconditions are satisfied. - Execute the minimal safe transition.
- Verify postconditions and publish an auditable result.
Failure modes: stale state, partial writes, race conditions, ambiguous output contracts.
Minimal concrete example
Plan -> dry-run -> execute -> verify -> rollback/forward-fix decision
Common misconceptions
- Assuming local success implies team-safe behavior.
- Treating policy violations as warnings instead of merge blockers.
- Skipping deterministic verification because the output appears correct.
Check-your-understanding questions
- Which invariant is most likely to break first under concurrency?
- What output proves your tool handled an edge case correctly?
- Where should enforcement happen: local hook, CI, or protected branch gate?
Check-your-understanding answers
- The invariant tied to mutable refs or policy-dependent merge eligibility.
- A deterministic transcript showing both success and controlled failure behavior.
- Layered enforcement: fast local checks plus non-bypassable server-side gates.
Real-world applications
- Change-management tooling for fast-moving teams.
- Incident-safe release workflows with traceable rollback paths.
- Compliance-ready source-control automation.
Where you’ll apply it This project and its immediate adjacent projects in this sprint.
References
- https://git-scm.com/docs
- https://dora.dev/capabilities/trunk-based-development/
Key insights
Git Log Formats is only valuable when its invariants are encoded into tooling and checks.
Summary
Mastering Git Log Formats here gives you transferable patterns for larger workflow systems.
Homework/Exercises to practice the concept
- Write one failing scenario and expected detection output.
- Define one invariant and one explicit violation test.
Solutions to the homework/exercises
- Use a stale branch or invalid metadata case and assert deterministic error reporting.
- Invariant: protected branch must not accept unchecked changes; violation test: bypass attempt should fail fast.
Software Engineering Metrics
Fundamentals
This concept matters in this project because your implementation will fail or become non-deterministic without a precise model of Software Engineering Metrics. You should define what the concept controls, what invariants must hold, and which actions are safe versus destructive. Treat this concept as a production concern, not a tutorial checkbox.
Deep Dive into the concept
When applying Software Engineering Metrics in this project, reason in three passes: data shape, state transitions, and enforcement. First, identify which artifacts are authoritative (commit objects, refs, metadata, policy config, CI status, or scan findings). Second, map how those artifacts change when your tool runs. Third, define failure behavior explicitly. In Git tooling, silent partial success is dangerous: you need either complete success with evidence or an explicit failure state with remediation guidance. Also account for scale behavior. A workflow that works on a toy repo may fail on large history depth, concurrent updates, or mixed branch policies. Include trace logs for every irreversible action, and separate simulation mode from write mode. For interview readiness, be able to explain how this concept protects delivery speed while reducing operational risk.
How this fit on projects
In this project, Software Engineering Metrics is directly used in design decisions, implementation constraints, and verification criteria.
Definitions & key terms
Software Engineering Metricsinvariant: A condition that must remain true before and after every operation.- Safety boundary: The point where actions become destructive unless guarded.
- Verification signal: Evidence proving the action behaved as expected.
Mental model diagram
Input state -> Validate invariant -> Apply change -> Verify output -> Record evidence
How it works
- Capture current state and constraints.
- Evaluate whether
Software Engineering Metricspreconditions are satisfied. - Execute the minimal safe transition.
- Verify postconditions and publish an auditable result.
Failure modes: stale state, partial writes, race conditions, ambiguous output contracts.
Minimal concrete example
Plan -> dry-run -> execute -> verify -> rollback/forward-fix decision
Common misconceptions
- Assuming local success implies team-safe behavior.
- Treating policy violations as warnings instead of merge blockers.
- Skipping deterministic verification because the output appears correct.
Check-your-understanding questions
- Which invariant is most likely to break first under concurrency?
- What output proves your tool handled an edge case correctly?
- Where should enforcement happen: local hook, CI, or protected branch gate?
Check-your-understanding answers
- The invariant tied to mutable refs or policy-dependent merge eligibility.
- A deterministic transcript showing both success and controlled failure behavior.
- Layered enforcement: fast local checks plus non-bypassable server-side gates.
Real-world applications
- Change-management tooling for fast-moving teams.
- Incident-safe release workflows with traceable rollback paths.
- Compliance-ready source-control automation.
Where you’ll apply it This project and its immediate adjacent projects in this sprint.
References
- https://git-scm.com/docs
- https://dora.dev/capabilities/trunk-based-development/
Key insights
Software Engineering Metrics is only valuable when its invariants are encoded into tooling and checks.
Summary
Mastering Software Engineering Metrics here gives you transferable patterns for larger workflow systems.
Homework/Exercises to practice the concept
- Write one failing scenario and expected detection output.
- Define one invariant and one explicit violation test.
Solutions to the homework/exercises
- Use a stale branch or invalid metadata case and assert deterministic error reporting.
- Invariant: protected branch must not accept unchecked changes; violation test: bypass attempt should fail fast.
Data Visualization
Fundamentals
This concept matters in this project because your implementation will fail or become non-deterministic without a precise model of Data Visualization. You should define what the concept controls, what invariants must hold, and which actions are safe versus destructive. Treat this concept as a production concern, not a tutorial checkbox.
Deep Dive into the concept
When applying Data Visualization in this project, reason in three passes: data shape, state transitions, and enforcement. First, identify which artifacts are authoritative (commit objects, refs, metadata, policy config, CI status, or scan findings). Second, map how those artifacts change when your tool runs. Third, define failure behavior explicitly. In Git tooling, silent partial success is dangerous: you need either complete success with evidence or an explicit failure state with remediation guidance. Also account for scale behavior. A workflow that works on a toy repo may fail on large history depth, concurrent updates, or mixed branch policies. Include trace logs for every irreversible action, and separate simulation mode from write mode. For interview readiness, be able to explain how this concept protects delivery speed while reducing operational risk.
How this fit on projects
In this project, Data Visualization is directly used in design decisions, implementation constraints, and verification criteria.
Definitions & key terms
Data Visualizationinvariant: A condition that must remain true before and after every operation.- Safety boundary: The point where actions become destructive unless guarded.
- Verification signal: Evidence proving the action behaved as expected.
Mental model diagram
Input state -> Validate invariant -> Apply change -> Verify output -> Record evidence
How it works
- Capture current state and constraints.
- Evaluate whether
Data Visualizationpreconditions are satisfied. - Execute the minimal safe transition.
- Verify postconditions and publish an auditable result.
Failure modes: stale state, partial writes, race conditions, ambiguous output contracts.
Minimal concrete example
Plan -> dry-run -> execute -> verify -> rollback/forward-fix decision
Common misconceptions
- Assuming local success implies team-safe behavior.
- Treating policy violations as warnings instead of merge blockers.
- Skipping deterministic verification because the output appears correct.
Check-your-understanding questions
- Which invariant is most likely to break first under concurrency?
- What output proves your tool handled an edge case correctly?
- Where should enforcement happen: local hook, CI, or protected branch gate?
Check-your-understanding answers
- The invariant tied to mutable refs or policy-dependent merge eligibility.
- A deterministic transcript showing both success and controlled failure behavior.
- Layered enforcement: fast local checks plus non-bypassable server-side gates.
Real-world applications
- Change-management tooling for fast-moving teams.
- Incident-safe release workflows with traceable rollback paths.
- Compliance-ready source-control automation.
Where you’ll apply it This project and its immediate adjacent projects in this sprint.
References
- https://git-scm.com/docs
- https://dora.dev/capabilities/trunk-based-development/
Key insights
Data Visualization is only valuable when its invariants are encoded into tooling and checks.
Summary
Mastering Data Visualization here gives you transferable patterns for larger workflow systems.
Homework/Exercises to practice the concept
- Write one failing scenario and expected detection output.
- Define one invariant and one explicit violation test.
Solutions to the homework/exercises
- Use a stale branch or invalid metadata case and assert deterministic error reporting.
- Invariant: protected branch must not accept unchecked changes; violation test: bypass attempt should fail fast.
3. Project Specification
3.1 What You Will Build
A dashboard that analyzes repository history to show contribution patterns, code hotspots, team dynamics, and technical debt indicators—like a mini version of GitPrime or Pluralsight Flow.
3.2 Functional Requirements
- Scope control: Deliver a deterministic and testable implementation.
- Correctness: Preserve Git invariants and policy constraints.
3.3 Non-Functional Requirements
- Performance: Deterministic execution with documented runtime behavior on representative history sizes.
- Reliability: Repeated runs on the same input produce identical outputs.
- Usability: Clear CLI or report output for both success and failure cases.
3.4 Example Usage / Output
You’ll have a dashboard that reveals repository insights:
Example Output:
$ repo-analytics /path/to/repo --period "last 6 months"
=== Repository Analytics Dashboard ===
📊 OVERVIEW
─────────────────────────────────────────
Repository: awesome-project
Period: Jul 2024 - Jan 2025 (6 months)
Commits: 847
Contributors: 12
Lines changed: +45,231 / -12,847
📈 COMMIT ACTIVITY
─────────────────────────────────────────
Monthly commits:
Jul ████████████████████ 156
Aug ████████████████ 132
Sep ███████████████████ 148
Oct ██████████████████████ 178
Nov ███████████████ 121
Dec ██████████ 82 (holiday season)
Jan ████████ 30 (partial month)
Peak day: Tuesdays (avg 8.2 commits/day)
Quietest: Weekends (avg 0.8 commits/day)
👥 TOP CONTRIBUTORS
─────────────────────────────────────────
alice ████████████████ 287 commits (34%)
bob ██████████ 178 commits (21%)
charlie ████████ 142 commits (17%)
diana ██████ 98 commits (12%)
others ████ 142 commits (16%)
🔥 CODE HOTSPOTS (most frequently changed)
─────────────────────────────────────────
src/api/handlers.ts Modified 47 times by 6 authors
src/core/parser.ts Modified 38 times by 4 authors
src/utils/validation.ts Modified 35 times by 8 authors
⚠️ High churn files may indicate:
- Complex logic needing simplification
- Missing tests causing bugs
- Feature instability
📉 TECHNICAL DEBT INDICATORS
─────────────────────────────────────────
TODO/FIXME comments added: 23
TODO/FIXME comments removed: 8
Net debt: +15 (growing)
Large commits (>500 lines): 12
"WIP" or "fix" commits: 34
Merge conflicts resolved: 28
Reverted commits: 4
🔀 MERGE PATTERNS
─────────────────────────────────────────
Merge commits: 89
Squash merges: 156
Rebase merges: 42
Average PR size: 127 lines
Average review time: 1.8 days
PRs merged without review: 12 (7%)
📁 FILE TYPE DISTRIBUTION
─────────────────────────────────────────
TypeScript: 67% (24,521 LOC)
JSON: 12% (4,891 LOC)
Markdown: 8% (3,211 LOC)
YAML: 5% (1,678 LOC)
Other: 8%
3.5 Data Formats / Schemas / Protocols
Describe input repository assumptions, output report shape, and any policy/config schema consumed by the tool.
3.6 Edge Cases
- Empty repository or shallow clone state.
- Detached HEAD or rewritten history during execution.
- Invalid metadata/policy configuration.
3.7 Real World Outcome
You’ll have a dashboard that reveals repository insights:
Example Output:
$ repo-analytics /path/to/repo --period "last 6 months"
=== Repository Analytics Dashboard ===
📊 OVERVIEW
─────────────────────────────────────────
Repository: awesome-project
Period: Jul 2024 - Jan 2025 (6 months)
Commits: 847
Contributors: 12
Lines changed: +45,231 / -12,847
📈 COMMIT ACTIVITY
─────────────────────────────────────────
Monthly commits:
Jul ████████████████████ 156
Aug ████████████████ 132
Sep ███████████████████ 148
Oct ██████████████████████ 178
Nov ███████████████ 121
Dec ██████████ 82 (holiday season)
Jan ████████ 30 (partial month)
Peak day: Tuesdays (avg 8.2 commits/day)
Quietest: Weekends (avg 0.8 commits/day)
👥 TOP CONTRIBUTORS
─────────────────────────────────────────
alice ████████████████ 287 commits (34%)
bob ██████████ 178 commits (21%)
charlie ████████ 142 commits (17%)
diana ██████ 98 commits (12%)
others ████ 142 commits (16%)
🔥 CODE HOTSPOTS (most frequently changed)
─────────────────────────────────────────
src/api/handlers.ts Modified 47 times by 6 authors
src/core/parser.ts Modified 38 times by 4 authors
src/utils/validation.ts Modified 35 times by 8 authors
⚠️ High churn files may indicate:
- Complex logic needing simplification
- Missing tests causing bugs
- Feature instability
📉 TECHNICAL DEBT INDICATORS
─────────────────────────────────────────
TODO/FIXME comments added: 23
TODO/FIXME comments removed: 8
Net debt: +15 (growing)
Large commits (>500 lines): 12
"WIP" or "fix" commits: 34
Merge conflicts resolved: 28
Reverted commits: 4
🔀 MERGE PATTERNS
─────────────────────────────────────────
Merge commits: 89
Squash merges: 156
Rebase merges: 42
Average PR size: 127 lines
Average review time: 1.8 days
PRs merged without review: 12 (7%)
📁 FILE TYPE DISTRIBUTION
─────────────────────────────────────────
TypeScript: 67% (24,521 LOC)
JSON: 12% (4,891 LOC)
Markdown: 8% (3,211 LOC)
YAML: 5% (1,678 LOC)
Other: 8%
4. Solution Architecture
4.1 High-Level Design
Inputs -> Validation -> Core Engine -> Output Formatter -> Verification Report
4.2 Key Components
| Component | Responsibility | Key Decisions |
|---|---|---|
| Input loader | Discover commits/refs/config inputs | Deterministic ordering and clear failure messages |
| Core engine | Compute project-specific logic | Separate read-only simulation from mutating actions |
| Reporter | Produce user-facing output and evidence | Include machine-readable and human-readable forms |
4.4 Data Structures (No Full Code)
ProjectState { refs, commits, policy, findings, metrics }
Result { status, evidence, warnings, next_actions }
4.4 Algorithm Overview
- Collect state from repository and configuration.
- Evaluate invariants and policy preconditions.
- Execute core transformation or analysis logic.
- Verify postconditions and emit deterministic report.
Complexity Analysis:
- Time: O(history + affected scope)
- Space: O(active graph window + report size)
5. Implementation Guide
5.1 Development Environment Setup
Use the environment defined in the main guide. Pin tool versions and fixture data to keep outputs reproducible.
5.2 Project Structure
project-root/
├── fixtures/
├── src/
├── tests/
├── docs/
└── README.md
5.3 The Core Question You’re Answering
“What does Git history reveal about a team’s development practices and code health?”
Before you write any code, sit with this question. Every commit tells a story—patterns in commits, authors, file changes, and timing reveal how a team works, where problems lurk, and what might need attention.
5.4 Concepts You Must Understand First
Stop and research these before coding:
- Git Log Formats
- What fields can you extract from git log?
- How do you use
--formatfor custom output? - How do you efficiently iterate through large histories?
- Book Reference: “Pro Git” Ch. 2.3 — Chacon
- Software Engineering Metrics
- What’s code churn and why does it matter?
- What’s bus factor and how do you calculate it?
- What metrics indicate healthy vs. unhealthy repos?
- Book Reference: “Software Engineering at Google” Ch. 7 — Winters et al.
- Data Visualization
- How do you choose the right chart type?
- How do you present trends over time?
- How do you make terminal-based visualizations?
- Resource: Matplotlib / D3.js documentation
5.5 Questions to Guide Your Design
Before implementing, think through these:
- Data Collection
- What git commands give you the data you need?
- How do you handle repositories with millions of commits?
- How do you normalize data across different time periods?
- Metric Calculation
- What metrics are genuinely useful vs. vanity metrics?
- How do you account for different commit styles (small vs. large)?
- How do you identify outliers (bot commits, merges, etc.)?
- Presentation
- Should output be terminal, HTML, or JSON?
- How do you make insights actionable?
- What warnings or recommendations should you provide?
5.6 Thinking Exercise
Analyze a Real Repository
Pick an open source repository and analyze manually:
# Clone a popular project
git clone https://github.com/microsoft/vscode --depth 1000
# Analyze
git log --format="%H|%an|%ae|%at|%s" --numstat | head -100
git shortlog -sn | head -10
git log --since="6 months ago" --oneline | wc -l
Questions while analyzing:
- Who are the top contributors?
- What files change most frequently?
- What patterns do you see in commit messages?
- What would you want to know about this project’s health?
5.7 The Interview Questions They’ll Ask
Prepare to answer these:
- “What metrics would you track to measure developer productivity?”
- “How would you identify technical debt from Git history?”
- “What does high code churn indicate, and is it always bad?”
- “How would you calculate the ‘bus factor’ for a repository?”
- “What insights can you derive from merge patterns?”
5.8 Hints in Layers
Hint 1: Starting Point
Use git log --format="%H|%an|%at|%s" --numstat to get commits with file stats. Parse the output into structured data.
Hint 2: Performance
For large repos, use --since and --until to limit scope. Process in streams, don’t load everything into memory.
Hint 3: Hotspot Detection Count how often each file appears in commits. Files with high counts AND multiple authors are likely complex.
Hint 4: Terminal Charts Use Unicode block characters (▁▂▃▄▅▆▇█) for simple bar charts. Libraries like asciichart can help.
5.9 Books That Will Help
| Topic | Book | Chapter |
|---|---|---|
| Git log | “Pro Git” by Chacon | Ch. 2.3 |
| Software metrics | “Software Engineering at Google” by Winters et al. | Ch. 7 |
| Data visualization | “The Visual Display of Quantitative Information” by Tufte | Ch. 1-3 |
5.10 Implementation Phases
Phase 1: Foundation (1-2 sessions)
- Define fixtures, expected outputs, and invariant checks.
- Build read-only analysis path.
Phase 2: Core Functionality (2-4 sessions)
- Implement project-specific core logic and deterministic reporting.
- Add policy and edge-case handling.
Phase 3: Polish and Edge Cases (1-2 sessions)
- Add failure demos, performance notes, and usability improvements.
- Finalize docs and validation transcripts.
5.11 Key Implementation Decisions
| Decision | Options | Recommendation | Rationale |
|---|---|---|---|
| Execution mode | direct write vs dry-run+write | dry-run+write | Safer and easier to debug |
| Output contract | free text vs structured+text | structured+text | Better automation and readability |
| Enforcement location | local only vs local+CI | local+CI | Prevents bypass in shared branches |
6. Testing Strategy
6.1 Test Categories
- Unit tests for parsing and policy logic.
- Integration tests on fixture repositories.
- Edge-case tests for stale refs, malformed metadata, and large histories.
6.2 Critical Test Cases
- Deterministic golden-path scenario.
- Policy violation hard-fail scenario.
- Recovery path after partial or conflicting state.
6.3 Test Data
Use fixed repository fixtures with known commit graphs and expected outputs stored under version control.
7. Common Pitfalls & Debugging
Problem 1: “Output looks correct but history or metadata is inconsistent”
- Why: Validation happens after mutation, not before.
- Fix: Add a preflight invariant check and a post-write verification step.
- Quick test: Run the same command twice on the same fixture and verify identical results.
Problem 2: “Tool works on small repo but times out on larger history”
- Why: Full traversal is performed where selective traversal is possible.
- Fix: Cache intermediate graph lookups and scope analysis to affected commits/paths.
- Quick test: Compare runtime on small and large fixtures with a clear budget target.
Problem 3: “Policy check can be bypassed by local-only behavior”
- Why: Enforcement is advisory, not server-authoritative.
- Fix: Mirror critical checks in CI and protected branch rules.
- Quick test: Attempt merge with failing policy in CI and confirm hard block.
8. Extensions & Challenges
8.1 Beginner Extensions
- Add richer error messages with remediation hints.
- Add fixture generation helpers for repeatable demos.
8.2 Intermediate Extensions
- Add performance instrumentation and budget assertions.
- Add policy configuration profiles by repository type.
8.3 Advanced Extensions
- Add distributed execution support for large repositories.
- Add signed evidence exports for compliance workflows.
9. Real-World Connections
9.1 Industry Applications
- Internal developer portals.
- Enterprise repository governance systems.
- Release safety and incident diagnostics tooling.
9.2 Related Open Source Projects
- Git core: https://git-scm.com/
- GitHub CLI: https://github.com/cli/cli
- pre-commit framework: https://pre-commit.com/
9.3 Interview Relevance
This project prepares you for architecture and debugging interviews that focus on merge policy, CI gates, and workflow reliability tradeoffs.
10. Resources
10.1 Essential Reading
- Pro Git (Internals and Workflows chapters)
- Software Engineering at Google (Version control and build chapters)
- Accelerate (delivery performance practices)
10.2 Video Resources
- Git internals talks from Git Merge conference archives.
- DORA and delivery metrics conference sessions.
10.3 Tools and Documentation
- https://git-scm.com/docs
- https://docs.github.com/
- https://dora.dev/
10.4 Related Projects in This Series
- Previous: 12: “Git Worktree Manager — Work on Multiple Branches Simultaneously
- Next: 14: “Git Secret Scanner — Find and Remove Leaked Credentials
11. Self-Assessment Checklist
11.1 Understanding
- I can explain the primary invariant this project enforces.
- I can explain one failure mode and one safe recovery path.
11.2 Implementation
- Functional requirements are met on deterministic fixtures.
- Critical edge cases are tested and documented.
11.3 Growth
- I can describe tradeoffs in an interview setting.
- I documented what I would change in a production version.
12. Submission / Completion Criteria
Minimum Viable Completion:
- Deterministic golden-path output exists.
- One failure scenario is handled with clear output.
- Core workflow objective is demonstrably met.
Full Completion:
- Minimum criteria plus policy validation, structured reporting, and edge-case coverage.
Excellence:
- Full completion plus measurable performance budget and production-hardening notes.