bibtex regression: does not write files outside of $CWD

[Ralf Treinen <treinen@free.fr>]

Hello TeX maintainers,

there seems to be a regression in the behaviour of bibtex: it refuses to
write to files outside of the current directory:

% ls -l oss.bib
-rw-r--r-- 1 rt rt 11879 Apr  1 09:01 oss.bib
% cat /tmp/bib2htmlf8c96b.aux
\relax
\bibstyle{plain}
\citation{*}
\bibdata{oss}
% bibtex /tmp/bib2htmlf8c96b.aux

bibtex: Not writing to /tmp/bib2htmlf8c96b.blg (openout_any = p).
I couldn't open file name `/tmp/bib2htmlf8c96b.blg'


This is texlive-latex-base 2011.20120322-1. Is this a bug or a feature?
It causes a bug in bibtex2html, see #666572. Google gave me pointers where
on this possible behaviour of bibtex:

http://tug.org/pipermail/tlbuild/2010q1/001304.html

-Ralf.

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