Support shell syntax

[drallgood]

Right now, the CMD is specified in exec form no matter what.
This means, that you can't really use variables in you command (adding sh -cto the beginning doesn't always work).

It would be nice if you could choose between shell and exec form.

[akobiakov]

Agree with @drallgood: current way of parsing the "command" field looks a bit odd and counterintuitive for a docker user. I'd prefer a syntax which looks similar to official docker forms for CMD (shell/exec). Something like:

<command>
    <shell>java -jar /opt/demo/server.jar</shell>
</command>

and

<command>
    <exec>java</exec>
    <params>
        <param>-jar</param>
        <param>/opt/demo/server.jar</param>
    </params>
</command>

What do you think, guys?

[drallgood]

I like the first one better. It's easier to create/read.

Implementation-wise, the easiest solution would be to just check for "sh -c" in the command and use the shell-syntax in case it's found.

[rhuss]

I like @akobiakov suggestion, since it is more explicit. I always hesitate a bit trying to be too "clever" (here: changing the Dockerfile syntax depending on the value a user gives). Also, having dedicate param tags would make it easier to provide args with spaces (don't know how well quoting works within Dockerfiles).

I would introduce this for 0.12.0 since it requires a (slight) configuration syntax change.

[drallgood]

Awesome! :)

[rhuss]

Well, if anyone wants to work on that, it would be awesome :) I'm happy for each PR since I still have quite some other stuff to work on for 0.11.3 ;-) Please see this document for how to contribute (but you probably already know this). And please let us know in this issue if some of you starts to work on this (in order to avoid duplicate efforts).

[akobiakov]

Due to a bug in dockerfile parser we have to use a shell format which is currently not supported by the plugin, so an external Dockerfile is the only workaround for now.
Therefore, I'd be glad to undertake this enhancement.

[rhuss]

Perfect, simply submit a PR when you are done, I will happily review and apply it ;-)

Thanks!

[alan-czajkowski]

I've reported a similar issue here: #149

I describe in detail why sh -c does not work (according to Docker documentation), and how to make it work -- which the plugin does not support.

[alan-czajkowski]

is there an ETA on this? would be nice to have this feature (as I don't like the Spotify Maven Docker plugin)

[akobiakov]

@alan-czajkowski We're working on it. My colleague is going to create a PR tomorrow.

[akobiakov]

The PR is here: https://github.com/rhuss/docker-maven-plugin/pull/156

[rhuss]

Cool ;-) 'hope that I can review and merge it in ASAP, hopefully this week.

[alan-czajkowski]

awesome work guys, once 0.12.0 comes out then i will test it out and #149 may become an obsolete issue

[rhuss]

Yeah, finally in in 0.12.0. 'will be released this week, stay tuned .... ;-)

Thanks again for your support and you patience ...