allow additional data files

Author: DoubleMalt

README.md

@@ -22,6 +22,16 @@ access to environment variables.
 - Call `meta-compose` and it will create a docker-compose.yml in the current
   directory
 
+```
+usage: meta-compose [-h] [-d DATAFILE]
+
+optional arguments:
+  -h, --help            show this help message and exit
+  -d DATAFILE, --datafile DATAFILE
+                        Use to specify data files in addition to meta-compose-
+                        data.yml. They must be JSON or YAML files.
+```
+
 ## Syntax of meta-compose.yml
 
 - Everything in basic [Jinja2](http://jinja.pocoo.org/) is allowed.

metacompose/cli/main.py

@@ -2,27 +2,37 @@
 import os
 import yaml
 from jinja2 import Environment, FileSystemLoader, StrictUndefined
+import argparse
 
 def env_override(value, key):
   return os.getenv(key, value)
 
 def main():
 
+    parser = argparse.ArgumentParser()
+
     template_file_name = "meta-compose.yml"
-    data_file_name = "meta-compose-data.yml"
+    data_file_names = ["meta-compose-data.yml"]
 
-    jinja = Environment(loader=FileSystemLoader("."), undefined=StrictUndefined)
+    parser.add_argument(
+      "-d", "--datafile", action='append',
+      help="Use to specify data files in addition to meta-compose-data.yml."
+           " They must be JSON or YAML files.")
 
-    jinja.filters['env'] = env_override
+    args = parser.parse_args()
 
+    data_file_names += args.datafile
+
+    jinja = Environment(loader=FileSystemLoader("."), undefined=StrictUndefined)
+    jinja.filters['env'] = env_override
     template = jinja.get_template(template_file_name)
 
+    data = {}
+    for data_file_name in data_file_names:
+        if os.path.isfile(data_file_name):
+            with open(data_file_name, "r") as fh:
+                data.update(yaml.safe_load(fh))
 
-    if os.path.isfile(data_file_name):
-        with open(data_file_name, "r") as fh:
-            data = yaml.safe_load(fh)
-    else:
-        data = {}
 
     composition = template.render(data)