ambrevar/storage: have subpath accept lists as well.

.local/share/common-lisp/source/ambrevar/storage.lisp

@@ -21,14 +21,16 @@
                                 (cmd:$cmd "findmnt -n --fstab --output TARGET --json")))))))
 
 (defun subpath (root &rest subdirs)
+  "Return merged paths as a string.
+SUBDIRS can be either a single path or a list of paths."
   (str:join (fof:separator)
-            (cons root subdirs)))
+            (cons root (alex:flatten subdirs))))
 
 (defun personal (&rest subdirs)
-  (apply #'subpath (uiop:getenv "PERSONAL") subdirs))
+  (subpath (uiop:getenv "PERSONAL") subdirs))
 
 (defun home (&rest subdirs)
-  (apply #'subpath (uiop:getenv "HOME") subdirs))
+  (subpath (uiop:getenv "HOME") subdirs))
 
 (defun basename (pathname)
   (first (last (pathname-directory (uiop:ensure-directory-pathname pathname)))))
@@ -80,11 +82,11 @@ If DESTINATION ends with '.gpg', it gets GPG-encrypted."
 (defun write-roots-index (&optional (destination (personal "index")))
   "Write indexes of `roots' sub-directories to DESTINATION."
   (labels ((write-simple-index (target &rest destination-subdir)
-             (write-index target (apply #'subpath destination
-                                        (append
-                                         destination-subdir
-                                         (list
-                                          (str:concat (fof:basename target) ".index"))))))
+             (write-index target (subpath destination
+                                          (append
+                                           destination-subdir
+                                           (list
+                                            (str:concat (fof:basename target) ".index"))))))
            (index1 (root)
              (ambrevar/shell:make-directory destination)
              (alex:mappend