Squashed commit of the following:

commit 4f053a06c1e9e3f63fd5afde60322f676acbdf45
Merge: 9177380 07a99ea
Author: Viktor Petersson <[email protected]>
Date:   Thu Jul 30 14:37:16 2015 +0100

    Merge branch 'master' into fixes

commit 9177380
Author: Viktor Petersson <[email protected]>
Date:   Thu Jul 30 14:00:51 2015 +0100

    Tweaks exception message.

commit 6a5832e
Author: Viktor Petersson <[email protected]>
Date:   Thu Jul 30 13:17:32 2015 +0100

    Simplifies logic as per feedback.

commit f750edd
Author: Viktor Petersson <[email protected]>
Date:   Thu Jul 30 11:09:14 2015 +0100

    Move return from list to dict. Adds exception handling.

commit 8e50f57
Author: Viktor Petersson <[email protected]>
Date:   Thu Jul 30 10:15:58 2015 +0100

    Reverts change to .gitignore.

commit 5ba2c1b
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 21:15:21 2015 +0100

    Fixes feedback. Adds three unittests.

commit e1c719e
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 17:00:16 2015 +0100

    WIP Adds test for parse_env_file

commit 4448ae7
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 16:42:49 2015 +0100

    Excludes coverage files.

commit 19a5d01
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 16:42:42 2015 +0100

    Switch fixes logic.

commit a8094c6
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 11:45:56 2015 +0100

    Implements logic for envfile parsing from Docker-cli

    Ref: https://github.com/docker/docker/blob/master/opts/envfile.go#L19-L51

commit ea9bfd9
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 11:41:23 2015 +0100

    Replaces CSV module with manual splitting.

commit a001d28
Author: Viktor Petersson <[email protected]>
Date:   Wed Jul 29 11:35:37 2015 +0100

    Removes isinstance on filename.

commit 419d596
Author: Viktor Petersson <[email protected]>
Date:   Tue Jul 28 22:39:33 2015 +0100

    Reflects @aanand's feedback.

commit e81e3c8
Author: Viktor Petersson <[email protected]>
Date:   Tue Jul 28 15:43:32 2015 +0100

    Typo fix.

commit 2898389
Author: Viktor Petersson <[email protected]>
Date:   Tue Jul 28 15:41:08 2015 +0100

    Refs #565. Adds minimal implementation of env_file client-side support.

Author: vpetersson

docker/utils/__init__.py

@@ -2,7 +2,7 @@
     compare_version, convert_port_bindings, convert_volume_binds,
     mkbuildcontext, tar, parse_repository_tag, parse_host,
     kwargs_from_env, convert_filters, create_host_config,
-    create_container_config, parse_bytes, ping_registry
+    create_container_config, parse_bytes, ping_registry, parse_env_file
 ) # flake8: noqa
 
 from .types import Ulimit, LogConfig # flake8: noqa

docker/utils/utils.py

@@ -518,6 +518,32 @@ def create_host_config(
     return host_config
 
 
+def parse_env_file(env_file):
+    """
+    Reads a line-separated environment file.
+    The format of each line should be "key=value".
+    """
+    environment = {}
+
+    with open(env_file, 'r') as f:
+        for line in f:
+
+            if line[0] == '#':
+                continue
+
+            parse_line = line.strip().split('=')
+            if len(parse_line) == 2:
+                k = parse_line[0]
+                v = parse_line[1]
+                environment[k] = v
+            else:
+                raise errors.DockerException(
+                    'Invalid line in environment file {0}:\n{1}'.format(
+                        env_file, line))
+
+    return environment
+
+
 def create_container_config(
     version, image, command, hostname=None, user=None, detach=False,
     stdin_open=False, tty=False, mem_limit=None, ports=None, environment=None,
@@ -528,6 +554,7 @@ def create_container_config(
 ):
     if isinstance(command, six.string_types):
         command = shlex.split(str(command))
+
     if isinstance(environment, dict):
         environment = [
             six.text_type('{0}={1}').format(k, v)

docs/api.md

@@ -234,6 +234,27 @@ from. Optionally a single string joining container id's with commas
  'Warnings': None}
 ```
 
+### parse_env_file
+
+A utility for parsing an environment file.
+
+The expected format of the file is as follows:
+
+```
+USERNAME=jdoe
+PASSWORD=secret
+```
+
+The utility can be used as follows:
+
+```python
+>> import docker.utils
+>> my_envs = docker.utils.parse_env_file('/path/to/file')
+>> docker.utils.create_container_config('1.18', '_mongodb', 'foobar',  environment=my_envs)
+```
+
+You can now use this with 'environment' for `create_container`.
+
 ## diff
 
 Inspect changes on a container's filesystem

tests/utils_test.py

@@ -1,12 +1,13 @@
 import os
 import os.path
 import unittest
+import tempfile
 
 from docker.client import Client
 from docker.errors import DockerException
 from docker.utils import (
     parse_repository_tag, parse_host, convert_filters, kwargs_from_env,
-    create_host_config, Ulimit, LogConfig, parse_bytes
+    create_host_config, Ulimit, LogConfig, parse_bytes, parse_env_file
 )
 from docker.utils.ports import build_port_bindings, split_port
 from docker.auth import resolve_repository_name, resolve_authconfig
@@ -17,6 +18,17 @@
 class UtilsTest(base.BaseTestCase):
     longMessage = True
 
+    def generate_tempfile(self, file_content=None):
+        """
+        Generates a temporary file for tests with the content
+        of 'file_content' and returns the filename.
+        Don't forget to unlink the file with os.unlink() after.
+        """
+        local_tempfile = tempfile.NamedTemporaryFile(delete=False)
+        local_tempfile.write(file_content.encode('UTF-8'))
+        local_tempfile.close()
+        return local_tempfile.name
+
     def setUp(self):
         self.os_environ = os.environ.copy()
 
@@ -95,6 +107,28 @@ def test_kwargs_from_env(self):
         except TypeError as e:
             self.fail(e)
 
+    def test_parse_env_file_proper(self):
+        env_file = self.generate_tempfile(
+            file_content='USER=jdoe\nPASS=secret')
+        get_parse_env_file = parse_env_file(env_file)
+        self.assertEqual(get_parse_env_file,
+                         {'USER': 'jdoe', 'PASS': 'secret'})
+        os.unlink(env_file)
+
+    def test_parse_env_file_commented_line(self):
+        env_file = self.generate_tempfile(
+            file_content='USER=jdoe\n#PASS=secret')
+        get_parse_env_file = parse_env_file((env_file))
+        self.assertEqual(get_parse_env_file, {'USER': 'jdoe'})
+        os.unlink(env_file)
+
+    def test_parse_env_file_invalid_line(self):
+        env_file = self.generate_tempfile(
+            file_content='USER jdoe')
+        self.assertRaises(
+            DockerException, parse_env_file, env_file)
+        os.unlink(env_file)
+
     def test_convert_filters(self):
         tests = [
             ({'dangling': True}, '{"dangling": ["true"]}'),