Eli Schwartz authored Apr 15, 2018 and Lukas Fleischer committed Apr 22, 2018

In the process, rename config.proto to config.defaults (because that is
what it is now).

Also use dict.get('key', default_value) when querying os.environ, rather
than an if block, as it is more pythonic/readable/concise, and reduces
the number of dict lookups.

This change allows aurweb configuration to be done via either:
- copying config.defaults to config and modifying values
- creating a new config only containing modified values, next to a
  config.defaults containing unmodified values

The motivation for this change is to enable ansible configuration in our
flagship deployment by storing only changed values, and deferring to
config.defaults otherwise.

A side benefit is, it is easier to see what has changed by inspecting
only the site configuration file.

If a config.defaults file does not exist next to $AUR_CONFIG or in
$AUR_CONFIG_DEFAULTS, it is ignored and *all* values are expected to
live in the modified config file.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

Since d4fe77ac

 (Reorganize Git interface scripts, 2016-10-08), the key
components of the aurweb SSH interface are installed system-wide. Update
the default configuration path to point to a central location.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

Instead of using relative imports, add support for installing the config
and db Python modules to a proper location using setuptools. Change all
git-interface scripts to access those modules from the search path.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

Introduce a new environment variable that can be used to specify the
path to an aurweb configuration file. If the environment variable is
unset, the default search path is used.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

Add a new module that automatically locates the configuration file and
provides methods to obtain the values of configuration options.

Use the new module instead of ConfigParser everywhere.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>