manager: add configuration from environment

For the development web server the environment variable
``RUAUMOKO_SETTINGS`` may now optionally be set. If it is set, it points
to a configuration file which can be used to configure the webapp
settings including, but not limited to, the path to the ruaumoko
dataset.

README.md

@@ -24,6 +24,25 @@ the [GNU GPL 3](http://gplv3.fsf.org/) (see LICENSE).
 Python dependences may be found in `requirements.txt`. To run the downloader
 you will also require the `convert` command (from `imagemagick`).
 
+## Running a development webserver
+
+The ``ruaumoko-api`` command can be used to run a development web server.
+
+```console
+$ ruaumoko-api runserver
+```
+
+This will use the default configuration. To use a custom configuration to, for
+example, change the dataset location use the ``RUAUMOKO_SETTINGS`` environment
+variable:
+
+```console
+$ cat > ruaumoko-development.txt <<EOL
+ELEVATION_DIRECTORY=/path/to/your/dataset
+EOL
+$ RUAUMOKO_SETTINGS=ruaumoko-development.txt ruaumoko-api runserver
+```
+
 ## Dataset Format
 
 Throughout Ruaumoko, data is indexed latitude-first/row-first

ruaumoko/manager.py

@@ -1,9 +1,12 @@
 """Command-line utility to run/manage webapp."""
+import os
 
 from flask.ext.script import Manager
 from .api import app
 
 manager = Manager(app)
 
 def main():
+    if 'RUAUMOKO_SETTINGS' in os.environ:
+        app.config.from_envvar('RUAUMOKO_SETTINGS')
     manager.run()