Allow overriding user on the command line

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

We are testing on the behavior of how the busybox image is made which is
kind of tricky but hopefully that shouln't change.

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

fig/cli/main.py

@@ -276,6 +276,7 @@ class TopLevelCommand(Command):
                                   new container name.
             --entrypoint CMD      Override the entrypoint of the image.
             -e KEY=VAL            Set an environment variable (can be used multiple times)
+            -u --user USER        Run as specified user.
             --no-deps             Don't start linked services.
             --rm                  Remove container after run. Ignored in detached mode.
             -T                    Disable pseudo-tty allocation. By default `fig run`
@@ -320,6 +321,10 @@ class TopLevelCommand(Command):
 
         if options['--entrypoint']:
             container_options['entrypoint'] = options.get('--entrypoint')
+
+        if options['--user']:
+            container_options['user'] = options.get('--user')
+
         container = service.create_container(
             one_off=True,
             insecure_registry=insecure_registry,

tests/fixtures/user-figfile/fig.yml

@@ -0,0 +1,3 @@
+service:
+  image: busybox:latest
+  command: id

tests/integration/cli_test.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 import sys
 
+from docker.errors import APIError
 from six import StringIO
 from mock import patch
 
@@ -8,6 +9,7 @@ from .testcases import DockerClientTestCase
 from fig.cli.main import TopLevelCommand
 
 
+
 class CLITestCase(DockerClientTestCase):
     def setUp(self):
         super(CLITestCase, self).setUp()
@@ -217,6 +219,21 @@ class CLITestCase(DockerClientTestCase):
             u'/bin/echo helloworld'
         )
 
+    @patch('dockerpty.start')
+    def test_run_service_with_user_overridden(self, _):
+        name = 'service'
+        self.command.base_dir = 'tests/fixtures/user-figfile'
+        # NOTE(chmou): available in default busybox and has a shell
+        user = 'sshd'
+        args = ['run', '--user', user, name]
+
+        self.command.dispatch(args, None)
+
+        service = self.project.get_service(name)
+        container = service.containers(stopped=True, one_off=True)[0]
+        container.inspect()
+        self.assertEqual(user, container.dictionary['Config']['User'])
+
     @patch('dockerpty.start')
     def test_run_service_with_environement_overridden(self, _):
         name = 'service'