Add parent directories search for default compose-files

Does not change directory to the parent with the compose-file found.
Works like passing '--file' or setting 'COMPOSE_FILE' with absolute path.
Resolves issue #946.

Signed-off-by: Aleksandr Vinokurov <aleksandr.vin@gmail.com>

compose/cli/command.py

@@ -10,7 +10,7 @@ from .. import config
 from ..project import Project
 from ..service import ConfigError
 from .docopt_command import DocoptCommand
-from .utils import call_silently, is_mac, is_ubuntu
+from .utils import call_silently, is_mac, is_ubuntu, find_candidates_in_parent_dirs
 from .docker_client import docker_client
 from . import verbose_proxy
 from . import errors
@@ -18,6 +18,13 @@ from .. import __version__
 
 log = logging.getLogger(__name__)
 
+SUPPORTED_FILENAMES = [
+    'docker-compose.yml',
+    'docker-compose.yaml',
+    'fig.yml',
+    'fig.yaml',
+]
+
 
 class Command(DocoptCommand):
     base_dir = '.'
@@ -100,20 +107,10 @@ class Command(DocoptCommand):
         if file_path:
             return os.path.join(self.base_dir, file_path)
 
-        supported_filenames = [
-            'docker-compose.yml',
-            'docker-compose.yaml',
-            'fig.yml',
-            'fig.yaml',
-        ]
-
-        def expand(filename):
-            return os.path.join(self.base_dir, filename)
-
-        candidates = [filename for filename in supported_filenames if os.path.exists(expand(filename))]
+        (candidates, path) = find_candidates_in_parent_dirs(SUPPORTED_FILENAMES, self.base_dir)
 
         if len(candidates) == 0:
-            raise errors.ComposeFileNotFound(supported_filenames)
+            raise errors.ComposeFileNotFound(SUPPORTED_FILENAMES)
 
         winner = candidates[0]
 
@@ -130,4 +127,4 @@ class Command(DocoptCommand):
             log.warning("%s is deprecated and will not be supported in future. "
                         "Please rename your config file to docker-compose.yml\n" % winner)
 
-        return expand(winner)
+        return os.path.join(path, winner)