Optionally flag or checkpoint an autobackup file with a suffix

This is a feature request:

Is it possible to add a keyboard shortcut that would flag the autobackups file name with a suffix (a tiny comment) when saving the file. Over the course of a day, I end up with a couple dozen timestamped backups. Sometimes while editing, I immediately want to take a peek at a file I saved 20 minutes or 2 hours ago. If I had saved it with a flag/suffix, I can easily identify that.

The flag could be fixed e.g. `_checkpoint` or a user prompted string. The resulting autobackups directory would look like this :

```
mycode_09063.py
mycode_09073.py
mycode_11054.py
mycode_11172_removed_big_feature.py <- checkpoint / tag
mycode_12031.py
mycode_14300.py
mycode_15712_added_cool_stuff.py <- checkpoint / tag
mycode_16003.py
```