bash_completion: fix issue with subdirectories not being completed
Previously, if there was a directory between the file and first-level directory (e.g. 'bar' in
foo/bar/file), then bash_completion would only list 'foo/file' instead of 'foo/bar/file'.
This behavior was introduced in 80f3ae36f908 to fix spaces in file names. In
this patch, we keep that behavior while also fixing subdirectory completion by
reverting 80f3ae36f908 and instead add backslashes to whitespace manually. This
approach means adding the completion option 'nospace' since we do this manually
now.