feat: configurable auto-pruning, cross-session rewind, and settings command

[cullendotdev]

I built these changes for my own workflow, I wanted checkpoints to survive restarts and give me more control over retention. Opening a PR in case you're interested or want to take things in a similar direction. Happy to adjust or close if it's not a fit. No expectations either way.

Summary

Adds three user-facing features to pi-rewind while preserving full backward compatibility:

1. Configurable auto-pruning — users can opt out of the rolling 50-checkpoint window and keep old sessions
2. Cross-session checkpoint picker — when old sessions are kept, /rewind shows a two-step picker (session → checkpoint)
3. /rewind-settings — interactive menu to change config live, auto-saves to ~/.pi/agent/config/rewind.json

Problem

The original extension hard-coded a 50-checkpoint rolling window per session and unconditionally pruned all checkpoints from previous sessions on startup. There was no way to:

• Keep checkpoints across pi restarts for long-running projects
• Change the retention limit without editing source code

Solution

A RewindConfig file at ~/.pi/agent/config/rewind.json with three knobs, all defaulting to the original behavior:

{
  "maxCheckpoints": 50,          // 0 = unlimited, never prune
  "keepOldSessions": false,      // true = survive restarts, show cross-session picker
  "cleanupHintThreshold": 200    // show cleanup hint in footer when exceeded
}

Two new commands give users direct control:

Command	What it does
/rewind-settings	Interactive menu to change any config value — auto-saves immediately, no restart needed
/rewind-cleanup	Shows stats grouped by session, offers to prune old sessions or trim current to max

When keepOldSessions is enabled, the /rewind picker becomes a two-step flow: pick a session (grouped by date), then pick a checkpoint within it. The Esc+Esc shortcut shows current session + the most recent old session for quick access. Footer status shows a warning hint when checkpoints exceed the cleanup threshold.

Four new core functions (getCheckpointStats, pruneAllOldSessions, deleteCheckpointsBulk, diffCheckpoints) support the new commands and keep the two-layer architecture intact — all pure git, no pi dependency.

What changed

New files

• src/config.ts — RewindConfig interface, load from rewind.json, env var overrides (PI_REWIND_*)
• CHANGELOG.md

Behavioral changes

• /rewind picker becomes two-step when keepOldSessions is enabled
• Footer status shows cleanup hint at threshold (◆ N checkpoints (consider /rewind-cleanup))
• Toggling keepOldSessions off in /rewind-settings prunes old refs immediately
• Esc+Esc shortcut is cross-session aware (shows current + 1 most recent old session)

Testing

npx tsx tests/core.test.ts
# 26 tests, 0 failures (was 20)

New coverage: cross-session pruning (with UUID-in-ref-name parsing), bulk delete, checkpoint stats, diff output.

Notes

• pruneOldSessions / pruneAllOldSessions extract session IDs from ref names via UUID pattern matching. They only operate on checkpoints created through the standard flow (resume-{uuid}-{ts}, turn-{uuid}-{turn}-{ts}). Hand-crafted checkpoint IDs without embedded UUIDs will be skipped.
• Pi resolves /rewind before subcommands, so cleanup and settings are registered as standalone commands (rewind-cleanup, rewind-settings) rather than subcommands.