Fish should treat an empty directory name in CDPATH as the current directory

[hugomg]

In dash and bash, an empty directory name in CDPATH means the current working directory so setting CDPATH to :/ has the same meaning as setting it to .:/. Fish doesn't have this default though:

dash$ export CDPATH=":/"
dash$ cd Desktop      #this works
dash$ cd ..
dash$ fish # Now lets see what happens in fish
fish$ cd Desktop
cd: The directory “Desktop” does not exist

The motivation for me reporting this is that this problem is a bit similar to the problem in #2090. Other shells might append to the CDPATH using CDPATH=$CDPATH:/blah and that will leave a colon at the start if CDPATH is previously unset. In that case, when Fish breaks it down into an array the first element will be the empty string.

[ridiculousfish]

Why do they do that? Argh. Thanks for reporting this.

[hugomg]

Yeah, that behavior is not in the manual... My guess is that its there so CDPATH=$CDPATH:/blah works

[krader1961]

This is going to be slightly harder to fix than I initially thought. That's because the places which iterate over CDPATH use class wcstokenizer which ignores (i.e., does not return) empty fields. So set CDPATH '' /some/dir is equivalent to set CDPATH /some/dir. There are only five uses of wcstokenizer and at least three of them are wrong in light of this issue. So I'm leaning towards removing that class and switching all five uses to tokenize_variable_array(). There should not be two ways to tokenize a fish array from its string form to an actual array/vector. Thoughts, @ridiculousfish?