My team’s been working on a new feature in Sourcegraph called code monitoring that can do things like this (and a whole lot more) with our search query language. It’s pretty simple:

1. Customise our starting point with the file of your choice: https://docs.sourcegraph.com/code_monitoring/how-tos/startin...

2. Create a new code monitor at https://sourcegraph.com/code-monitoring

Whenever the file changes, you’ll get an email notification.