bug#36372: 27.0.50; replace-regexp-in-string skips START first chars in return value

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Tue, 25 Jun 2019 14:01:49 +0200
> 
>  (replace-regexp-in-string "a" "X" "abcab" t t nil 2)
> 
> would be expected to return
> 
>  "abcXb"
> 
> but the actual return value is
> 
>  "cXb"
> 
> This was probably not intended. The manual text is
> 
>  This function copies STRING and searches it for matches for REGEXP,
>  and replaces them with REP.  It returns the modified copy.  If
>  START is non-‘nil’, the search for matches starts at that index in
>  STRING, so matches starting before that index are not changed.
> 
> The question is whether it is too late to fix the bug, or if it needs to be 
> documented.

Both, I think ;-)

Thanks.