Specify revisions to save from auto delete
Google Drive automatically deletes older revisions that are no longer of interest to the user. To prevent this from happening, you can set the boolean flag
true to mark revisions that you don't want Drive to purge.
Download a revision
You can use the value of the
headRevisionId field from the Files resource to download the latest revision.
This fetches the revision that corresponds to the metadata of the file you previously retrieved. To download the data for all previous revisions of the file that are still stored in cloud, you can call
revisions.list, which gets all the revisionIds.
revisions.getmethod with the parameter
alt=media. Revisions for Google Docs, Sheets, and Slides can't be downloaded.
Google Docs, Drawings, and Slides revisions auto-increment the revision numbers. However, series of numbers may have gaps if revisions are deleted, so you should not rely on sequential numbers when you retrieve revisions.
Publish a revision
To publish a Google Docs, Sheets, and Slides revision, you set the
published property for that file in the Revisions property.
If the file is created in a G Suite domain, the
publishedOutsideDomain property indicates whether the revision is accessible by anyone or if it is restricted to users of the domain.
Published revisions do not reflect changes made to a file unless the
publishAuto property is set. If that property is set to true, newer revisions of a file will be automatically published, overwriting the previous ones. This behavior is also controlled by the "Automatically re-publish when changes are made" checkbox in the Drive UI.