be less picky about XDG_DATA_HOME and HOME environment variable trailing slash

In fennel-ls.utils, there's a path-join function that has the logic
for joining paths and putting a slash in the middle if it's not already
there.

src/fennel-ls/docs.fnl

@@ -1,3 +1,4 @@
+(local {: path-join} (require :fennel-ls.utils))
 (local fennel (require :fennel))
 (local {:metadata METADATA
         :scopes {:global {:specials SPECIALS
@@ -5,9 +6,9 @@
   (require :fennel.compiler))
 
 (local docset-ext ".lua")
-(local data-dir (.. (or (os.getenv "XDG_DATA_HOME")
-                      (.. (or (os.getenv "HOME") "") "/.local/share"))
-                  "/fennel-ls/docsets/"))
+(local data-dir (path-join (or (os.getenv "XDG_DATA_HOME")
+                             (path-join (or (os.getenv "HOME") "") ".local/share"))
+                  "fennel-ls/docsets/"))
 
 (local specials
   (collect [name value (pairs SPECIALS)]

src/fennel-ls/utils.fnl

@@ -201,10 +201,10 @@ WARNING: this is only used in the test code, not in the real language server"
   (-> (.. path path-sep suffix)
     ;; delete duplicate
     ;; windows
-    (: :gsub "%.\\" "")
+    (: :gsub "^%.\\" "")
     (: :gsub "\\+" "\\")
     ;; modern society
-    (: :gsub "%./" "")
+    (: :gsub "^%./" "")
     (: :gsub "/+" "/")
     (->> (pick-values 1))))