gistfile1.txt

$ git --version
git version 2.8.0.rc3.226.g39d4020

$ ls -a
.  ..

$ mkdir -p foo/bar/; touch {,foo/,foo/bar/}{a,b,c}; echo '/*' > .gitignore;
$ find -type f | sort
./b
./a
./c
./foo/a
./foo/bar/a
./foo/bar/b
./foo/bar/c
./foo/b
./foo/c
./.gitignore

$ cat .gitignore
/*

$ git init
Initialized empty Git repository in /tmp/test/.git/

$ git status --porcelain --ignored --untracked-files=all          
!! .gitignore
!! a
!! b
!! c
!! foo/a
!! foo/b
!! foo/bar/a
!! foo/bar/b
!! foo/bar/c
!! foo/c

$ cat >> .gitignore
!/foo/bar/

$ cat .gitignore
/*
!/foo/bar/

$ git status --porcelain --ignored --untracked-files=all
?? .gitignore
?? a
?? c
!! b
!! foo/a
!! foo/b
!! foo/bar/a
!! foo/bar/b
!! foo/bar/c
!! foo/c