Hopefully this helps someone in the future. If you use this endpoint: https://community.jaspersoft.com/documentation/tibco-jasperreports-server-rest-api-reference/v710/resources-service#Searching_the_Repository it will return the attributes of the file, including the version of the existing file. The problem is that it's a search endpoint so you have to be really specific about the file that you are wanting otherwise it will return a list of files. Use fileUri= and q= options to pinpoint to the exact file you want info for. Note that this endpoint: https://community.jaspersoft.com/documentation/tibco-jasperreports-server-rest-api-reference/v710/resources-service#Viewing_Resource_Details Will return the object that you uploaded. Which, in my experience, if the file is a jrxml file it will return the actual jrxml file and it doesn't actually include the attributes of the file on the server (which is where the version is at).
I know this is old but it would probably be a good idea to post a link to the resource you're describing. https://community.jaspersoft.com/wiki/getting-started-rest-web-service-api
