Add self-update capability to epsilon

[jbouwman]

Summary

Epsilon should have the ability to check for updates and automatically update itself, similar to package managers like rustup, npm, or other self-updating tools.

Use Case

Currently, updating epsilon requires manual intervention. Users need to:

1. Check if new versions are available
2. Download/build new versions manually
3. Replace their installation

This creates friction for:

• Development workflows: Developers want to stay current with latest features/fixes
• CI/CD pipelines: Automated builds should be able to update epsilon as needed
• Distribution: Easier to distribute epsilon knowing users can easily update

Proposed Implementation

Add commands to the epsilon CLI:

Check for Updates

epsilon --check-updates
# Output: "New version 1.2.3 available (current: 1.2.1)"
# or: "Epsilon is up to date (1.2.1)"

Auto-Update

epsilon --update
# Downloads, builds, and installs latest version
# Provides progress feedback
# Backs up current version for rollback

Version Management

epsilon --version-info
# Shows current version, install location, update channel, etc.

epsilon --rollback  
# Rollback to previous version if update failed

Technical Considerations

Update Sources

• Primary: GitHub releases (https://github.com/jbouwman/epsilon/releases)
• Future: Custom update servers for enterprise deployments
• Channels: stable, beta, nightly (if applicable)

Security

• Verify signatures/checksums of downloaded updates
• Use HTTPS for all update communications
• Validate update packages before installation

Cross-Platform Support

• Handle different installation locations (~/.local/bin/ vs system paths)
• Support different architectures (x86_64, ARM64, etc.)
• Platform-specific update mechanisms (macOS, Linux, Windows)

Backup/Rollback

• Keep previous version for quick rollback
• Atomic updates (don't leave broken installations)
• Configuration preservation across updates

Implementation Phases

Phase 1: Basic Update Check

• Add version checking against GitHub API
• Simple --check-updates command
• JSON output option for scripting

Phase 2: Auto-Update

• Download and install updates
• Basic backup/rollback capability
• Progress indication

Phase 3: Advanced Features

• Multiple update channels
• Signature verification
• Enterprise update server support
• Selective component updates

Example Workflow

# Check for updates (exit code 0 = up to date, 1 = update available)
epsilon --check-updates

# Update if available
epsilon --update

# Verify update worked
epsilon --version

# Rollback if needed
epsilon --rollback

Integration Examples

CI/CD Usage

# GitHub Actions
- name: Update epsilon
  run: |
    epsilon --check-updates && epsilon --update || true
    epsilon --version

Development Workflow

# Daily development routine
epsilon --update  # Stay current
epsilon --load my-project.lisp

Benefits

1. User Experience: Frictionless updates encourage staying current
2. Security: Users get security fixes faster
3. Support: Easier to support when users are on recent versions
4. Distribution: Self-updating software is easier to distribute
5. CI/CD: Enables automated environment management

Related Tools

Similar functionality in other tools:

• rustup update (Rust toolchain)
• npm update -g npm (Node.js package manager)
• brew upgrade (Homebrew)
• apt update && apt upgrade (APT)

Configuration

Allow users to configure update behavior:

epsilon --config update.auto-check=true
epsilon --config update.channel=stable
epsilon --config update.frequency=weekly

This feature would significantly improve the epsilon user experience and adoption by removing friction from keeping installations current.