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add-incremental-endpoint

One sentence: Handles incremental chapter dependency tracking and manifest persistence for the repoforge build system.

Trigger: incremental or manifest operations

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Quick Reference

Task	Pattern
Load manifest	load_manifest(out_dir)
Get git SHA	get_git_sha(repo_root)
Check stale chapters	stale_chapter_names(changed_files, consumed_by_chapter)

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Critical Patterns (Detailed)

Pattern 1: Manifest Persistence

Load and save the manifest to track chapter state across incremental builds.

# Load existing manifest
manifest: Optional[Manifest] = load_manifest(out_dir)

# Save updated manifest after changes
save_manifest(out_dir, manifest)  # type: ignore

Pattern 2: Stale Chapter Detection

Identify which chapters need rebuilding after file changes by comparing dependencies.

# Detect chapters that are stale due to changed files
stale: list[str] = stale_chapter_names(changed_files, consumed_by_chapter)

When to Use

• After git operations to determine which chapters need rebuilding
• When file changes invalidate chapter dependencies
• Before running incremental builds to skip up-to-date chapters

Commands

# Run incremental build
python -m repoforge.cli build --incremental

# Check git state
python -c "from repoforge.incremental import get_git_sha; print(get_git_sha(Path('.')))"

Anti-Patterns

Don't: Skip dependency tracking

# BAD: Assuming no chapters are stale without checking dependencies
stale = []  # Wrong: never empty if files changed

# BAD: Missing manifest persistence
save_manifest(out_dir, manifest)  # Required after chapter changes

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