If a branch named "bisect" or "new-bisect" already was created in the
repo by other means than git bisect, doing a git bisect used to override
the branch without a warning. Now if the branch "bisect" or
"new-bisect" already exists, and it was not created by git bisect itself,
git bisect start fails with an appropriate error message. Additionally,
if checking out a new bisect state fails due to a merge problem, git
bisect cleans up the temporary branch "new-bisect".
The accidental override has been noticed by Andres Salomon, reported
through
http://bugs.debian.org/478647
Signed-off-by: Gerrit Pape <pape@smarden.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>