Now that spawn assumes executeFile takes a String containing utf8 codepoints
(and takes an actual String as input) adjust Prompt.Shell to avoid double
encoding. U.Run functions are updated to be consistent with spawn.
* true error: more modules export foldl/foldl'/foldr, so explicitly use the Data.Foldable one
* -Werror error: transition from Control.OldException to Control.Exception, assuming everything was IOException
doesDirectoryExist returns True if given an empty string using ghc <= 6.10.4.
This causes getDirectoryContents to raise an exception and X.P.Shell does not
render. This is only an issue if you have an empty string in your PATH.
Using ghc == 6.12.1, doesDirectoryExist returns False given an empty string, so
this should not be an issue in the future.
The helper function asks the shell for the value of a variable, else returns the second argument.
getBrowser and getEditor obviously specialize it for two particular possibly queries
