Support multiple files in COMPOSE_FILE env var.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

compose/cli/command.py

@@ -58,8 +58,10 @@ def get_config_path_from_options(options):
     if file_option:
         return file_option
 
-    config_file = os.environ.get('COMPOSE_FILE')
+    config_files = os.environ.get('COMPOSE_FILE')
-    return [config_file] if config_file else None
+    if config_files:
+        return config_files.split(os.pathsep)
+    return None
 
 
 def get_client(verbose=False, version=None):

docs/reference/envvars.md

@@ -27,10 +27,15 @@ defaults to the `basename` of the project directory. See also the `-p`
 
 ## COMPOSE\_FILE
 
-Specify the file containing the compose configuration. If not provided,
+Specify the path to a Compose file. If not provided, Compose looks for a file named
-Compose looks for a file named  `docker-compose.yml` in the current directory
+`docker-compose.yml` in the current directory and then each parent directory in
-and then each parent directory in succession until a file by that name is
+succession until a file by that name is found.
-found. See also the `-f` [command-line option](overview.md).
+
+This variable supports multiple compose files separate by a path separator (on
+Linux and OSX the path separator is `:`, on Windows it is `;`). For example:
+`COMPOSE_FILE=docker-compose.yml:docker-compose.prod.yml`
+
+See also the `-f` [command-line option](overview.md).
 
 ## COMPOSE\_API\_VERSION
 

tests/unit/cli/command_test.py

@@ -1,16 +1,19 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
+import os
+
 import pytest
 from requests.exceptions import ConnectionError
 
 from compose.cli import errors
 from compose.cli.command import friendly_error_message
+from compose.cli.command import get_config_path_from_options
+from compose.const import IS_WINDOWS_PLATFORM
 from tests import mock
-from tests import unittest
 
 
-class FriendlyErrorMessageTestCase(unittest.TestCase):
+class TestFriendlyErrorMessage(object):
 
     def test_dispatch_generic_connection_error(self):
         with pytest.raises(errors.ConnectionErrorGeneric):
@@ -21,3 +24,31 @@ class FriendlyErrorMessageTestCase(unittest.TestCase):
             ):
                 with friendly_error_message():
                     raise ConnectionError()
+
+
+class TestGetConfigPathFromOptions(object):
+
+    def test_path_from_options(self):
+        paths = ['one.yml', 'two.yml']
+        opts = {'--file': paths}
+        assert get_config_path_from_options(opts) == paths
+
+    def test_single_path_from_env(self):
+        with mock.patch.dict(os.environ):
+            os.environ['COMPOSE_FILE'] = 'one.yml'
+            assert get_config_path_from_options({}) == ['one.yml']
+
+    @pytest.mark.skipif(IS_WINDOWS_PLATFORM, reason='posix separator')
+    def test_multiple_path_from_env(self):
+        with mock.patch.dict(os.environ):
+            os.environ['COMPOSE_FILE'] = 'one.yml:two.yml'
+            assert get_config_path_from_options({}) == ['one.yml', 'two.yml']
+
+    @pytest.mark.skipif(not IS_WINDOWS_PLATFORM, reason='windows separator')
+    def test_multiple_path_from_env_windows(self):
+        with mock.patch.dict(os.environ):
+            os.environ['COMPOSE_FILE'] = 'one.yml;two.yml'
+            assert get_config_path_from_options({}) == ['one.yml', 'two.yml']
+
+    def test_no_path(self):
+        assert not get_config_path_from_options({})