config: add DCOS_DIR env var (#939)

cli/dcoscli/data/help/dcos.txt

@@ -25,10 +25,13 @@ Options:
 Environment Variables:
     DCOS_CONFIG
         Set the path to the DC/OS configuration file. By default, this variable
-        is set to ~/.dcos/dcos.toml.
+        is set to $DCOS_DIR/dcos.toml.
     DCOS_DEBUG
         Indicates whether to print additional debug messages to stdout. By
         default this is set to false.
+    DCOS_DIR
+        Set the data directory for DC/OS configuration. By default, this
+        variable is set to ~/.dcos
     DCOS_LOG_LEVEL
         Prints log messages to stderr at or above the level indicated. This is
         equivalent to the --log-level command-line option.

dcos/config.py

@@ -22,6 +22,17 @@ def get_config_path():
     return os.environ.get(constants.DCOS_CONFIG_ENV, get_default_config_path())
 
 
+def get_config_dir_path():
+    """
+    :returns: path to the DC/OS data directory
+    :rtype: str
+    """
+
+    config_dir = os.environ.get(constants.DCOS_DIR_ENV) or \
+        os.path.join("~", constants.DCOS_DIR)
+    return os.path.expanduser(config_dir)
+
+
 def get_default_config_path():
     """Returns the default path to the DCOS config file.
 
@@ -29,10 +40,7 @@ def get_default_config_path():
     :rtype: str
     """
 
-    return os.path.expanduser(
-        os.path.join("~",
-                     constants.DCOS_DIR,
-                     'dcos.toml'))
+    return os.path.join(get_config_dir_path(), 'dcos.toml')
 
 
 def get_config(mutable=False):

dcos/constants.py

@@ -1,5 +1,8 @@
 DCOS_DIR = ".dcos"
-"""DC/OS data directory.  Can store subcommands and the config file."""
+"""DC/OS data directory. Can store subcommands and the config file."""
+
+DCOS_DIR_ENV = 'DCOS_DIR'
+"""Name of the environment variable pointing to the DC/OS data directory"""
 
 DCOS_SUBCOMMAND_ENV_SUBDIR = 'env'
 """In a package's directory, this is the cli contents subdirectory."""

dcos/subcommand.py

@@ -13,7 +13,7 @@ from distutils.version import LooseVersion
 
 import requests
 
-from dcos import constants, util
+from dcos import config, constants, util
 from dcos.errors import DCOSException
 from dcos.subprocess import Subproc
 
@@ -358,10 +358,10 @@ def install(pkg):
 
 
 def _subcommand_dir():
-    """ Returns ~/.dcos/subcommands """
-    return os.path.expanduser(os.path.join("~",
-                                           constants.DCOS_DIR,
-                                           constants.DCOS_SUBCOMMAND_SUBDIR))
+    """ Returns subcommand dir. defaults to ~/.dcos/subcommands """
+
+    return os.path.join(config.get_config_dir_path(),
+                        constants.DCOS_SUBCOMMAND_SUBDIR)
 
 
 def _package_dir(name):