fix: don't use $functions_source for compatibility with zsh < 5.4

plugins/aliases/aliases.plugin.zsh

@@ -1,11 +1,14 @@
-# with lots of 3rd-party amazing aliases installed, just need something to explore it quickly.
-#
-# - acs: alias cheatsheet
-#   group alias by command, pass addition argv to grep.
-function acs(){
-  (( $+commands[python3] )) || {
-    echo "[error] No python executable detected"
-    return
+# Handle $0 according to the standard:
+# https://zdharma-continuum.github.io/Zsh-100-Commits-Club/Zsh-Plugin-Standard.html
+0="${${ZERO:-${0:#$ZSH_ARGZERO}}:-${(%):-%N}}"
+0="${${(M)0:#/*}:-$PWD/$0}"
+
+eval '
+  function acs(){
+    (( $+commands[python3] )) || {
+      echo "[error] No python executable detected"
+      return
+    }
+    alias | python3 "'"${0:h}"'/cheatsheet.py" "$@"
   }
-  alias | python3 ${functions_source[$0]:h}/cheatsheet.py $@
-}
+'