EXPOSE ports not analysed correctly about dockerfilelint

[thomasbiddle]

Along with this - it would be great to allow a variable to be referenced. I follow the practice of

ENV PORT=3000
EXPOSE $PORT

... (Use in other spots as well, to keep DRY)

Line 18: EXPOSE $PORT
Issue  Category      Title                 Description
    1  Possible Bug  Invalid Port Exposed  Exposing ports should only be valid port numbers.

[marccampbell]

@thomasbiddle Agreed. Will you open a new issue for the ENV PORT; EXPOSE $PORT pattern? I think we should add this in, but we should also do it correctly and ensure that the env var is set and still a valid value (when possible).

[thomasbiddle]

@marccampbell Referenced in #86.

[nexdrew]

Closing this as it should be fixed in version 1.3.0+. Please let us know if you still have problems with the "port/proto" syntax.

(Also note that fromlatest.io isn't currently running the latest version of dockerfilelint, see replicatedhq/fromlatest.io#242.)