docs: reorganize threading and branch filtering sections

[shuhuiluo]

• Move implemented threading sections into new "Threading & Branch Filtering" section
• Add "PR Comment Branch Filtering" section (in-memory cache approach)
• Add "Base Branch Change (Retarget) Handling" for retroactive anchor creation
• Update table references: event_threads → messageMappings
• Update "Remaining Work" checklist with current status
• Remove obsolete SQL snippets, keep implementation details concise

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Updated implementation plan for thread-based event grouping and branch-specific filtering features
  • Added architecture guidance, configuration examples, and event processing workflows
  • Enhanced documentation for feature interactions with existing subscription capabilities

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[coderabbitai]

Walkthrough

This PR updates GITHUB_APP_IMPLEMENTATION_PLAN.md to formalize and expand architectural documentation. It introduces new structured sections for Branch-Specific Event Filtering and Thread-Based Event Grouping, including syntax specifications, data models, and implementation guidance. The PR reorganizes previous brainstorm content into concrete implementation details, updates configuration examples, and adjusts implementation status indicators to reflect completed work and revised priorities.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

• Documentation-only changes to a single file with no code modifications
• Reorganization and clarification of architectural concepts rather than entirely new content
• Reviewers should verify technical accuracy of the threading and branch-filtering specifications, particularly the data model descriptions and configuration examples
• Ensure consistency with any existing implementation across referenced features

Possibly related PRs

• docs: add branch-specific filtering and thread grouping brainstorms #69: Introduces overlapping thread-based event grouping and branch-specific filtering designs with similar documentation and data model proposals
• docs: add roadmap for PR anchor updates, mentions, and label filters #84: Updates the same GitHub app documentation covering threading, anchor updates, and label/branch-based event filtering features
• docs: add GitHub App implementation plan #25: Original PR introducing GITHUB_APP_IMPLEMENTATION_PLAN.md, which this PR extends with additional architectural sections and refinements

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'docs: reorganize threading and branch filtering sections' accurately and concisely describes the main change in the pull request, which involves reorganizing documentation sections related to threading and branch filtering.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch docs/threading-branch-filtering

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

GITHUB_APP_IMPLEMENTATION_PLAN.md (2)

432-443: Add language identifier to fenced code block.

The "Event Processing Flow" code block should declare its language for proper syntax highlighting and linting compliance.

 2. **Event Processing Flow:**
 
-```
+```text
 Incoming webhook event
   ↓
 Is this a PR/issue event?

---

507-519: Use markdown heading instead of emphasis for section title.

Convert the emphasis formatting to a proper markdown heading for consistent document structure.

-**Solution: In-memory PR Branch Cache**
+### Solution: In-memory PR Branch Cache

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 8819efc and e1f7b52.

📒 Files selected for processing (1)

• GITHUB_APP_IMPLEMENTATION_PLAN.md (2 hunks)

🧰 Additional context used

🪛 LanguageTool

GITHUB_APP_IMPLEMENTATION_PLAN.md

[uncategorized] ~389-~389: The official name of this software platform is spelled with a capital “H”.
Context: ...orage:** New branch_filter column in github_subscriptions: - NULL = default bra...

(GITHUB)

🪛 markdownlint-cli2 (0.18.1)

GITHUB_APP_IMPLEMENTATION_PLAN.md

433-433: Fenced code blocks should have a language specified

(MD040, fenced-code-language)

---

507-507: Emphasis used instead of a heading

(MD036, no-emphasis-as-heading)

🔇 Additional comments (2)

GITHUB_APP_IMPLEMENTATION_PLAN.md (2)

355-585: Threading & Branch Filtering section is comprehensive and well-integrated.

The new sections are clearly structured, technically sound, and align with PR objectives. Key strengths:

• Branch-Specific Event Filtering: Clear syntax, thorough scope table, design decisions justified, migration impact noted
• Thread-Based Event Grouping: Comprehensive data model, detailed event flow, practical edge cases covered, configuration options explicit
• PR Comment Branch Filtering: Smart cache strategy with API fallback documented
• PR Anchor Dynamic Updates: Well-thought-out anchor refresh logic, base branch retargeting handled, webhook ordering considerations included
• messageMappings consistently referenced (no stale event_threads references)
• Breaking change (default branch-only) explicitly called out at lines 402–405

The content strikes a good balance between implementation detail and conciseness.

---

641-644: Remaining Work section properly reflects implementation status.

The checklist correctly marks completed items (thread-based grouping, PR anchor updates) and pending items (PR comment branch filtering, retroactive anchor creation). Status accurately reflects the new section content.