pr-explainer

name	pr-explainer
description	Explain a PR's purpose, motivation, and architectural context with ASCII diagrams. Use when the user wants to understand what a PR does, why it exists, how it fits into the system, or asks for a visual summary of changes. Triggers on "explain this PR", "what does this PR do", "summarize this branch", "show me what changed", or `/pr-explainer`.

PR Explainer

Overview

Produce a first-principles explanation of a PR (or current branch diff) that builds understanding incrementally. A reader who has never seen the codebase should be able to follow the explanation and understand not just what changed, but why each piece exists and how the pieces interact.

Output is structured top-down: problem first, then mechanism, then details. All diagrams use ASCII box-and-arrow art so they render correctly in any terminal. Do NOT use Mermaid — the primary consumer is the CLI, not GitHub.

Input Detection

1. Argument is a PR number or URL → use gh pr view <arg> --json title,body,baseRefName and gh pr diff <arg>
2. No argument → diff the current branch against main:
   • git log main..HEAD --oneline for commit history
   • git diff main...HEAD for the full diff
   • git diff main...HEAD --stat for a file summary

Workflow

Step 1: Gather the Diff

Collect the raw material:

# For current branch (no argument):
git diff main...HEAD --stat          # file-level summary
git diff main...HEAD                 # full diff
git log main..HEAD --oneline         


gh  view <number> --json title,body,baseRefName,headRefName
gh  diff <number>