The `vcsh delete` command fails to remove files that have spaces in their filenames

[hanjianwei]

Here are the steps to reproduce this bug：

vcsh init foobar
touch 'foo bar'
vcsh foobar add 'foo bar'
vcsh foobar commit -m 'Add files'
vcsh foobar delete

The foo bar file still exists. It might be necessary to set a new IFS, similar to what is done in the write_gitignore command.