Don't use a function variable in alias

This conditionally set a function variable in an unsafe way.

If you do something like

```fish
if condition
   set -f foo bar
end
```

then, if the condition was false, $foo could still use a global variable.

In this case, alias would now fail if a variable $wraps was defined globally.

This reverts most of commit 14458682d9.

The message rewording can stay, it's *fine* (tho it'll break the
translations but then we'd need a real string freeze with a
translation team for those to be worth anything anyway, soo)

share/functions/alias.fish

@@ -1,6 +1,6 @@
 function alias --description 'Creates a function wrapping a command'
     set -l options h/help s/save
-    argparse --max-args=2 $options -- $argv
+    argparse -n alias --max-args=2 $options -- $argv
     or return
 
     if set -q _flag_help
@@ -55,18 +55,17 @@ function alias --description 'Creates a function wrapping a command'
         else
             set prefix command
         end
-    else
-        # Do not define wrapper completion if we have "alias foo 'foo xyz'" or "alias foo 'sudo foo'"
-        # This is to prevent completions from recursively calling themselves (#7389).
-        # The latter will have rare false positives but it's more important to
-        # prevent recursion for this high-level command.
-        if test $last_word != $name
-            set -f wraps --wraps (string escape -- $body)
-        end
     end
     set -l cmd_string (string escape -- "alias $argv")
 
-
+    # Do not define wrapper completion if we have "alias foo 'foo xyz'" or "alias foo 'sudo foo'"
+    # This is to prevent completions from recursively calling themselves (#7389).
+    # The latter will have rare false positives but it's more important to
+    # prevent recursion for this high-level command.
+    set -l wraps
+    if test $first_word != $name; and test $last_word != $name
+        set wraps --wraps (string escape -- $body)
+    end
 
     echo "function $name $wraps --description $cmd_string; $prefix $body \$argv; end" | source
     if set -q _flag_save