Matt & Steve, thanks to the both of you for your answers so far!

I am using version 1.4+20091117 (and the matching TortoiseHg 0.9, although
it is completely unrelated to ToirtoiseHg as stated earlier.... the best
proof being that using the command line interface yields the same behaviour).

Excuse my asking, but whatever the patch one might well do in the module
supporting the HTTP protocol I really cannot see how one can possibly grab
the stderr of an external process launched by Python's subprocess.call() in
mercurial/hook.py. Could you explain shortly why this behaviour is
"intended, correct and standard"?

Again, I am talking about "external program" hooks (a.k.a. shell script)
here (so I am assuming that mercurial.hook._exthook() is getting called
here, not mercurial.hook._pythonhook().

Why not use one of the many popen variations instead and redirect stderr to
a file-like object which would write to ui?

Many thanks in advance
Best regards