fix: restore path based parsing in 4.0 (#566)

* fix: ensure dirs arent empty strings

This fixes issue 564 also safely wraps strings for parsing

[564]

* fix: scope parts variable to function

* chore: fix formatting

* fix: remove hacky length test, clean up join

credit to @scaryrawr where credit is due.

Author: nnungest

functions/_tide_parent_dirs.fish

@@ -1,7 +1,10 @@
 function _tide_parent_dirs --on-variable PWD
-    set -g _tide_parent_dirs (string escape (
-        for dir in (string split / -- $PWD)
-            set -la parts $dir
-            string join / -- $parts
-        end))
+    set -g _tide_parent_dirs (
+        string escape (
+            for dir in (string split / -- $PWD)
+                set -fa parts $dir
+                string join / -- $parts
+            end
+        )
+    )
 end