Keep locale settings in environment

Signed-off-by: Michal Čihař <michal@cihar.com>
Configure commiter before trying to commit
Support for checking status per file

Signed-off-by: Michal Čihař <michal@cihar.com>
Switch implementation to VCS backend

All VCS interaction should be now in separate module, which will allow
to add support for other VCSs in future.

Fixes #513

Signed-off-by: Michal Čihař <michal@cihar.com>
Make the method public

Signed-off-by: Michal Čihař <michal@cihar.com>