Nathan Collins [off-list ref] writes:
Example session:
$ git init test.git
Initialized empty Git repository in /tmp/test.git/.git/
$ cd test.git
$ mkdir "dir name"
$ touch dir\ name/file.txt
$ echo "dir\\ name/file.txt -text -whitespace" >> .git/info/attributes
$ git add dir\ name/file.txt
name/file.txt is not a valid attribute name: .git/info/attributes:1
That's because spaces are not allowed in paths there.
echo "dir?name/file.txt -text" >.git/info/attributes
may be an easy workaround for now.