test: add t7301 for git-clean--interactive

Add testcases for git-clean--interactive.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
zh_CN.po: translation for git-clean

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
debug: path_relative_checkout.c

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>