The eagerly awaited project history capability for Google Apps Script in now rolling out. The feature is similar to the version history functionality found in other Google Workspace editors like Google Docs. As well as being able to see differences between the current and previous versions you can restore your script project to that point. Unlike Docs, Sheets and Slides there is currently no ability to ‘make a copy’ or ‘name a version’. My experience when using the Drive revisions data is that Google may merge revisions to save storage space.
