Linus Torvalds [off-list ref] writes:
The syntax is
git bisect start <pathspec>
followed by all the normal "git bisect good/bad" stuff.
I love how I can just say "this might be interesting" and
find your message in my mailbox next morning [*1*] ;-).
This would be useful to cut down the number of bisection needed
to reach the culprit if the initial guess is correct as to which
part of the tree is involved.
[Reference]
*1* http://marc.theaimsgroup.com/?l=git&m=111669620826189