Add support for --user, improve tests.

Make the tests use nose instead of unittest, and use properly
parameterized arguments. This makes it a lot easier to see
what fails.

docker-rerun

@@ -60,6 +60,27 @@ class Container(object):
             self.args.extend([template % entry for entry in target])
 
 
+    def if_image_diff(self, selector, fallback):
+        """Gets a property if it's different from the image's config.
+
+        Compares the value of a property in the container's information to the
+        same property in the image information. If the value is different then
+        the container's version is returned, otherwise the specified fallback
+        is returned.
+
+        This is useful where the container inherits config from the image,
+        such as the command or the user to run as. We only want to include it
+        in the arguments if it has been explicitly changed.
+
+        Args:
+            selector (func): Function to extract the property.
+            fallback (object): Value to return if the properties are identical.
+        """
+        container = selector(self.info)
+        image = selector(self.image_info)
+        return fallback if container == image else container
+
+
 def docker_inspect(target, what):
     """Uses `docker inspect` to get details about the given container or image.
 
@@ -86,11 +107,7 @@ def handle_binds(container):
 
 def handle_command(container):
     """Copies the command (trailing arguments)."""
-    cont_cmd = container.info['Config']['Cmd']
-    image_cmd = container.image_info['Config']['Cmd']
-
-    if cont_cmd != image_cmd:
-        container.cmd = cont_cmd
+    container.cmd = container.if_image_diff(lambda c: c['Config']['Cmd'], [])
 
 
 def handle_image(container):
@@ -139,6 +156,13 @@ def handle_restart(container):
         container.args.append(arg)
 
 
+def handle_user(container):
+    """Copies the user (--user/-u) argument."""
+    user = container.if_image_diff(lambda c: c['Config']['User'], None)
+    if user:
+        container.args.append('--user=%s' % user)
+
+
 def handle_volumes_from(container):
     """Copies the volumes from (--volumes-from) argument."""
     container.add_args_from_list('--volumes-from=%s',

requirements.txt

@@ -1,3 +1,4 @@
 nose
+nose_parameterized
 pylint
 

test.py

@@ -1,37 +1,32 @@
 #!/usr/bin/python3
 
 import subprocess
-import unittest
-
-
-class RerunTest(unittest.TestCase):
-
-
-    def _run(self, cmd):
-        subprocess.call(cmd,
-                        stdout=subprocess.DEVNULL,
-                        stderr=subprocess.DEVNULL)
-
-
-    def test_command_matches(self):
-        commands = [
-            'docker run --name=test123 -d hello-world',
-            'docker run --name=test123 -d hello-world:latest',
-            'docker run --name=test123 -d hello-world /hello world...',
-            'docker run --name=test123 --restart=always -d hello-world',
-            'docker run --name=test123 --restart=on-failure:10 -d hello-world',
-            'docker run --name=test123 --net=host -d hello-world',
-            'docker run --name=test123 -d -p=127.0.0.1:443:443/tcp -p=127.0.0.1::1336/tcp hello-world',
-            'docker run --name=test123 -d -p=443/tcp hello-world',
-            'docker run --name=test123 --volume=/dev/null:/null --volume=/dev/urandom:/mnt/random -d hello-world',
-        ]
-
-        for command in commands:
-            with self.subTest(cmd=command):
-                self._run(['docker', 'rm', '-f', 'test123'])
-                self._run(command.split(' '))
-                output = subprocess.check_output(['./docker-rerun', '--dry-run', 'test123'])
-                output = output.decode('utf-8').strip().splitlines()
-                self.assertEqual(output[3], command)
-                self._run(['docker', 'rm', '-f', 'test123'])
+from nose_parameterized import parameterized
+
+
+def _run(cmd):
+    subprocess.call(cmd,
+                    stdout=subprocess.DEVNULL,
+                    stderr=subprocess.DEVNULL)
+
+
+@parameterized([
+    'docker run --name=test123 -d hello-world',
+    'docker run --name=test123 -d hello-world:latest',
+    'docker run --name=test123 -d hello-world /hello world...',
+    'docker run --name=test123 --restart=always -d hello-world',
+    'docker run --name=test123 --restart=on-failure:10 -d hello-world',
+    'docker run --name=test123 --net=host -d hello-world',
+    'docker run --name=test123 -d -p=127.0.0.1:443:443/tcp -p=127.0.0.1::1336/tcp hello-world',
+    'docker run --name=test123 -d -p=443/tcp hello-world',
+    'docker run --name=test123 --user=root -d hello-world /hello foobar',
+    'docker run --name=test123 --volume=/dev/null:/null --volume=/dev/urandom:/mnt/random -d hello-world',
+])
+def test_command_matches(command):
+    _run(['docker', 'rm', '-f', 'test123'])
+    _run(command.split(' '))
+    output = subprocess.check_output(['./docker-rerun', '--dry-run', 'test123'])
+    output = output.decode('utf-8').strip().splitlines()
+    assert output[3] == command
+    _run(['docker', 'rm', '-f', 'test123'])