In attempting my first HASSIO add-on following the “hello-world” noob developer guide, I ran into an issue with the build version number. I wanted to start my new app with version “.01”, but could not get the code to load. Kept getting 500 server error - “invalid reference format”. After much head scratching & debugging, this was due to starting the version with a decimal. Simply changing it to “0.01” solved the problem.
Not sure if this is worth submitting an issue report, but just in case some one else searches for this error message, maybe posting this will help them.
config.json
"name": "Hello World",
"version": ".01",
...
18-10-04 18:49:07 INFO (SyncWorker_12) [hassio.docker.addon] Start build local/armhf-addon-hello_world:.01
18-10-04 18:49:07 ERROR (SyncWorker_12) [hassio.docker.addon] Can't build local/armhf-addon-hello_world:.01: 500 Server Error: Internal Server Error ("invalid reference format")