Allow overriding user on the command line

[chmouel]

Allow overriding a user on the command line from the one specified in
the fig.yaml

Tests are a bit tricky since regenerating a docker image with multiple
users just for this is consuming so let's catch the error instead and
make sure it works.

Signed-off-by: Chmouel Boudjnah chmouel@chmouel.com

[aanand]

Nice, thanks.

• docker run supports both -u and --user - we should too.
• The test seems to be failing: https://app.wercker.com/#buildstep/5491bae16b3ba8733d8f148d
• I don't think the test needs to check the output of the command - just inspect the created container and check it's got the right value for "User".

[chmouel]

Thanks @aanand, great suggestions

[IanVS]

@chmouel, this would be an awesome feature. Do you think you'll have a chance to finish it up? If not, I could take a crack at it. It looks like it's pretty darn close.

[chmouel]

@IanVS feel free to take it over :)

[IanVS]

OK I think I have something that will work, but I'm not sure how to structure the assert of the test. To get the "User" as @aanand suggests, what should I do? container.user doesn't exist, and it seems neither does container.dictionary['Config']['User']

What's the right way to do this? Thanks!

[IanVS]

@chmouel, I couldn't figure out how to use your commit directly, so I created a new pull request,#971 . Hope that's alright. I'm new to contributing to OSS, still learning the ropes.

[bfirsh]

Replaced by #971. Thanks!