Add git_config module (#1945)
Add git_config module (#1945)

* Add git_config module

This module can be used for reading and writing git configuration at all
three scopes (local, global and system). It supports --diff and --check
out of the box.

This module is based off of the following gist:
https://gist.github.com/mgedmin/b38c74e2d25cb4f47908
I tidied it up and added support for the following:
- Reading values on top of writing them
- Reading and writing values at any scope
The original author is credited in the documentation for the module.

* Respond to review feedback

- Improve documentation by adding choices for parameters, requirements
  for module, and add missing description for scope parameter.
- Fail gracefully when git is not installed (followed example of puppet
  module).
- Remove trailing whitespace.

* Change repo parameter to type 'path'

This ensures that all paths are automatically expanded appropriately.

* Set locale to C before running commands to ensure consistent error messages

This is important to ensure error message parsing occurs correctly.

* Adjust comment

thaim/ansible,thaim/ansible