Now, a filename to hide that is specified without a path separator will
count as hidden if it appears in any component of the file path (not
only the last component); semantically, this means hiding a file by only
its name (without any part of a path) will hide both files and folders,
e.g. hiding ".git" will hide "/.git" and also "/.git/foo".
We also do prefix matching so that hiding "/.git" will hide "/.git"
and "/.git/foo" but not "/.gitignore".
The remaining logic is a globular match like before.