Support building multiple Kaniko variants (executor, debug, warmer) from single repository

[kingdonb]

Priority: High (Required for complete Kaniko support)

Description:
Kaniko has multiple build targets in its Makefile (make images includes executor, debug, warmer, etc.) but the current directory-based system assumes one image per directory. Need to design enhanced build-config.yaml format to support multiple targets.

Current Limitation:

• kaniko/ directory only builds debug variant
• Need all Kaniko variants for complete replacement
• Directory naming becomes awkward (kaniko-executor/, kaniko-debug/)

Proposed Solution:
Enhanced build-config.yaml with targets array:

upstream_repo: https://github.com/chainguard-dev/kaniko
upstream_ref: v1.25.3
dockerfile_path: deploy/Dockerfile

targets:
  - name: executor
    target: executor
    additional_tags: [latest, v1.25.3]
  - name: debug  
    target: debug
    additional_tags: [debug-latest, debug-v1.25.3]

Source Documents (for cleanup consideration):

• /AGENTS.md - Lines 159-171 (Issue 3: Multi-Target Kaniko Builds)
• /SPEC.md - Lines 160-180 (Kaniko-Specific Considerations)

Research Required:

• Examine Kaniko Makefile structure
• Identify all available build targets
• Design matrix build job generation
• Test with actual Kaniko repository

Acceptance Criteria:

• Enhanced build-config.yaml format implemented
• Multiple images generated from single repository
• All Kaniko variants (executor, debug, warmer) buildable
• Proper tagging for each variant
• Multi-arch support for all variants

[kingdonb]

🔬 RESEARCH COMPLETE: Kaniko Multi-Target Analysis

Makefile Analysis

Found 4 distinct Kaniko variants in the upstream Makefile:

# From kaniko Makefile
images:
    docker build ... -t $(REGISTRY)/executor:latest -f deploy/Dockerfile --target kaniko-executor .
    docker build ... -t $(REGISTRY)/executor:debug -f deploy/Dockerfile --target kaniko-debug .
    docker build ... -t $(REGISTRY)/executor:slim -f deploy/Dockerfile --target kaniko-slim .
    docker build ... -t $(REGISTRY)/warmer:latest -f deploy/Dockerfile --target kaniko-warmer .

Current Implementation

✅ Working: kaniko-debug target correctly implemented in kaniko/build-config.yaml

Multi-Target Challenge

Problem: Our directory-based system expects one image per directory, but Kaniko has 4 variants from the same source.

Design Options for Implementation

Option 1: Multiple Directories (Simple)

kaniko-executor/build-config.yaml  # target: kaniko-executor
kaniko-debug/build-config.yaml     # target: kaniko-debug  
kaniko-slim/build-config.yaml      # target: kaniko-slim
kaniko-warmer/build-config.yaml    # target: kaniko-warmer

Pros: Works with current pipeline
Cons: Duplicates upstream_repo/ref in 4 places

Option 2: Enhanced Config (Recommended)

# kaniko/build-config.yaml
targets:
  - name: executor
    target: kaniko-executor
    tags: [latest, v1.25.3]
  - name: debug  
    target: kaniko-debug
    tags: [debug, v1.25.3-debug]
  - name: slim
    target: kaniko-slim  
    tags: [slim, v1.25.3-slim]
  - name: warmer
    target: kaniko-warmer
    tags: [warmer, v1.25.3-warmer]

Pros: Single config, flexible tagging
Cons: Requires pipeline modifications

Option 3: Matrix Builds

Generate multiple build jobs from single directory config
Pros: Most flexible
Cons: Complex implementation

Next Steps

1. ✅ Validate kaniko-debug build works
2. 🎯 Choose multi-target approach
3. 📝 Implement chosen solution
4. 🧪 Test all 4 variants

Current Status: Ready to proceed once kaniko-debug build validates successfully!