Watchers

Poll external sources on an interval and react only to new items. Three ready-made scripts plus a shared watermark helper; wire them into a cron job (or run them ad-hoc from the terminal).

When to Use

• User wants to watch an RSS/Atom feed and be notified of new entries
• User wants to watch a GitHub repo's issues / pulls / releases / commits
• User wants to poll an arbitrary JSON endpoint and get notified on new items
• User asks for "a watcher for X" or "notify me when X changes"

Mental model

A watcher is just a script that:

1. Fetches data from the external source
2. Compares against a watermark file of previously-seen IDs
3. Writes the new watermark back
4. Prints new items to stdout (or nothing on no-change)