I *think* this was added because people tried to use set /p even though real dos didn't support that. Only the Windows command line did that. And to not have to deal with the recurring "why does set /p not work" the devs added the reply that you should use choice.
This is just how I think it is not entirely sure.

Yep, just googled it. The /p switch was introduced with Windows 2k.
So that's not a bug 😉

But yeah, you might be right that it checks too much. I should read more thoroughly what others write. Sorry

Ok, that explains the intention. This is fine with me, I don’t need the /p option. But the implementation is kind of, how do I say it politely … unfortunate. It breaks the main function of set because it’s not transparent. I cannot assign any string to a variable that contains “/p”.

Normally I would comment the two lines and compile, but I want to use SVN Daum version, and I don’t know where the repository is hosted and what prerequisites I need. So this better be fixed in the standard DOSbox SVN repository.

Where do I have to report this bug to get this done?

On the SF bug tracker. (Don't have a linkright now andnot where i can look it up)

https://sourceforge.net/p/dosbox/bugs/ <- bug tracker

Thanks. I see I had the correct bugtracker found, but I didn’t saw the milestone SVN in the list. So, bug is filed, now wait and see. 😀

Workaround for now:

set dircmd=/wp

mkvreak, Qbix just now relaxed the Set /p restrictions in SVN. Good call