bisect: no longer try to clean up left-over `.git/head-name` files
As per the code comment, the `.git/head-name` files were cleaned up for backwards-compatibility: an old version of `git bisect` could have left them behind. Now, just how old would such a version be? As of 0f497e75f05 (Eliminate confusing "won't bisect on seeked tree" failure, 2008-02-23), `git bisect` does not write that file anymore. Which corresponds to Git v1.5.4.4. Even if the likelihood is non-nil that there might still be users out there who use such an old version to start a bisection, but then decide to continue bisecting with a current Git version, it is highly improbable. So let's remove that code, at long last. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>