tests: parameterize --valgrind option
Running tests under helgrind and DRD recently proved useful in
tracking down thread interaction issues. This can unfortunately not
be done through GIT_VALGRIND_OPTIONS because any tool other than
memcheck would complain about unknown options.
Let --valgrind take an optional parameter that describes the valgrind
tool to invoke. The default mode is to run memcheck as before.
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>