Update https://wiki.ubuntu.com/Kernel/KernelBisection Inquiry

[Seth Forshee]

On Wed, Oct 17, 2012 at 07:44:46AM -0600, Tim Gardner wrote:
> Joe - you should probably mention in the wiki that bisecting across
> non-linear tags is usually a bad idea. Also some thoughts on gross
> bisection by installing the various upstream stable builds would be
> helpful. That narrows the bisection focus to upstream v.s. Ubuntu patches.

It would also be useful to add some information on how to tell whether
or not two given tags are non-linear. The following works, but maybe
someone else knows of a more elegant way to do it.

  $ git rev-list <newer-tag> | \
    grep $(git log --pretty=oneline -1 <older-tag> | cut -d' ' -f1)

If that command outputs a sha1 then the tags are linear, otherwise they
are not.