Add the 'isRoot' predicate

[mrkkrp]

This should return True when given path is root (upper level) directory.

[mrkkrp]

Depends on #18.

[sjakobi]

I'm surprised that I couldn't find an analogous function in either filepath or directory, indicating that maybe it isn't widely needed.

I'm not against adding it, but if it's added, I'd suggest adding it at some place where it doesn't distract from more useful functions.

[joehillen]

I feel like the problems described in #18 and #33 can be caught by expressing the special case for / at the type level rather than throw a runtime exception. I think this could be done in a fairly backwards compatible way. Give me a chance to test out the idea before merging anything.

[joehillen]

Nevermind, my idea wouldn't work without dependent types.

[sjakobi]

I'm surprised that I couldn't find an analogous function in either filepath or directory, indicating that maybe it isn't widely needed.

I overlooked System.FilePath.isDrive there. Not sure if we should also call our function isDrive then. It seems to me that calling a Windows drive like C:\\ a root is more common than calling the Posix root / a drive.

[emmanueltouzery]

I felt the need for this predicate for searching parent folders. Say you want to search for the .gitignore for a project. I would recursively look at the parent folder searching for the gitignore, until i reach the root folder. Seems like a pretty common use-case?