l10n: zh_CN: for git v2.20.0 l10n round 1 to 3

Translate 257 new messages (4187t0f0u) for git 2.20.0.

Reviewed-by: Zhou Fangyi <[email protected]>
Reviewed-by: 依云 <[email protected]>
Signed-off-by: Jiang Xin <[email protected]>

Author: jiangxin