tree cea2bfd5cdf2af19f8b8c6011201bdd81a759831
parent 4ccafd7a02fd9905cc5382b2c1d5abdb11a7525a
author Junio C Hamano <junkio@cox.net> 1130962667 -0800
committer Junio C Hamano <junkio@cox.net> 1130979058 -0800

Do not fail on hierarchical branch names.

"git-checkout -b frotz/nitfol master" failed to create
$GIT_DIR/refs/heads/frotz/nitfol but went ahead and updated
$GIT_DIR/HEAD to point at it, resulting in a corrupt repository.
Exit when we cannot create the new branch with an error status.

While we are at it, there is no reason to forbid subdirectories
in refs/heads, so make sure we handle that correctly.

Signed-off-by: Junio C Hamano <junkio@cox.net>