mailinfo: fix passing wrong address to git_mailinfo_config
git_mailinfo_config() expects "struct mailinfo *". But in
setup_mailinfo(), "mi" is already "struct mailinfo *". &mi would make
it "struct mailinfo **" and git_mailinfo_config() would damage some
other memory when it assigns some value to mi->use_scissors.
This is caught by t4150.20. git_mailinfo_config() breaks
mi->name.alloc and makes strbuf_release() in clear_mailinfo() attempt
to free strbuf_slopbuf.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>