PR Description Generator

Writes a GitHub PR title and description from the diff between two local git branches, focused on what reviewers need: purpose, key decisions/assumptions, behavioral or conceptual changes, and a brief testing note if relevant. Uses only standard git commands, so any agent can follow it.

1. Resolve branches

• Both named → use as given.
• Only one named → it's the base; target defaults to current branch.
• None named → base defaults to main, then master if main doesn't exist (git branch --list). Only check these two names — no scanning other branches, no guessing. If neither exists, stop and ask. Target defaults to current branch (git branch --show-current).

State the resolved base/target before proceeding.

2. Diff

• Confirm both branches exist (git branch --list <name>); stop if not.
• git diff <base>...<target> and git log <base>..<target> --oneline
• Empty diff → stop and say so, don't fabricate a description.

3. Analyze