update git-completion.bash and update git-prompt.sh

Signed-off-by: Wang Zhen <yuchen12@gmail.com>
dotbashrc: add GIT_PS1_SHOWCOLORHINTS=1

Signed-off-by: Wang Zhen <yuchen12@gmail.com>
modify dotbashrc

Signed-off-by: Wang Zhen <yuchen12@gmail.com>