Can you please sign your commits following these rules:

https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work

The easiest way to do this is to amend the last commit:

git commit --amend -s --no-edit && git push -f

LGTM

We should probably add a few integration tests to enforce the environment variables for a container or it maybe pretty easy to write a unit test for this method.

Yup, +1 to tests.

@crosbymichael @LK4D4 Thanks for the review. I will add tests shortly. One scenario that I am not very convinced about is that env for range may show differently, for example
docker run --name backend -p 7101:7101 -p 7102:7102 -p 7103-7105:7103-7105
<we get normal ENV variables for all 5 ports with this fix but the range env variables will look like below since we detect the continuity in allocation>
BACKEND_PORT_7101_TCP_PORT_END=7105
BACKEND_PORT_7101_TCP_PORT_START=7101

Please see that I added a unit test for check all env variables.

LGTM

@LK4D4 Anything else to add to this or can we merge?

Thanks for the tests!