Add script to create a guix environment based on a named environment template under ~/.config/guix.

genv

@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+import sys
+import os
+from subprocess import call
+
+ENV_NAME=sys.argv[1]
+ENV_COMMAND=sys.argv[2:]
+ENVS_DIR=os.path.join(os.path.expanduser("~"), ".config", "guix", "envs")
+
+env_packages = []
+with open(os.path.join(ENVS_DIR, ENV_NAME)) as env_def:
+    env_packages = env_def.read().strip().split(" ")
+
+call(["guix", "environment", "--ad-hoc"] + env_packages + ["--"] + ENV_COMMAND)