Ensure gh token is retrieved before submission steps (#1581)

src/alire/alire-publish-submit.adb

@@ -166,11 +166,20 @@ package body Alire.Publish.Submit is
    ---------------
 
    procedure Fork (Context : in out Data) is
+      use type UString;
    begin
       if not Ask_To_Fork (Context) then
             Raise_Checked_Error
               ("Cannot continue with automatic submission");
       end if;
+
+      --  If the fork already existed, the token wouldn't have been needed up
+      --  to this point, so now we make sure it is informed for next steps.
+
+      if Context.Token = "" then
+         Context.Token := +Ask_For_Token
+           ("to create a submission to the community index on your behalf");
+      end if;
    end Fork;
 
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