(In reply to comment #42)
> What exactly do I need to bisect i.e starting and ending commit ?

git bisect start
git bisect good <commit id or tag>
git bisect bad <commit id or tag>

At this point git will check out the commit halfway between these two.  Test it
and report back:
git bisect good //if that commit works
git bisect bad // if that commit is broken

git will checkout the next half way point.  repeat until it's done.  Once
you've found the problematic commit:

git bisect reset // resets your tree back to where you were before you started
bisecting.  E.g., if it was working in 3.12 and broke in 3.13:

git bisect start
git bisect good v3.12
git bisect bad v3.13