Rework GitRepository::status() and add StatusCommandBuilder.
Rework GitRepository::add() and add AddCommandBuilder.
Rework GitRepository::rm() and add RmCommandBuilder.
Rework GitRepository::commit() and add CommitCommandBuilder.
Rework GitRepository::tag() and add TagCommandBuilder.
Add GitRepository::show() and ShowCommandBuilder.
Rename BranchCommandBuilder::getList() into BranchCommandBuilder::getNames().
Rename RemoteCommandBuilder::getList() into RemoteCommandBuilder::getNames().
Remove obsolete constants from DescribeCommandBuilder.
Add GitRepository::log() and LogCommandBuilder.
Rework the README for the new API.