bisect: teach "skip" to accept special arguments like "A..B"

bisect: teach "skip" to accept special arguments like "A..B"

The current "git bisect skip" syntax is "git bisect skip [<rev>...]"
so it's already possible to skip a range of revisions using
something like:

$ git bisect skip $(git rev-list A..B)

where A and B are the bounds of the range we want to skip.

This patch teaches "git bisect skip" to accept:

$ git bisect skip A..B

as an abbreviation for the former command.

This is done by checking each argument to see if it contains two
dots one after the other ('..'), and by expending it using
"git rev-list" if that is the case.

Note that this patch will not make "git bisect skip" accept all
that "git rev-list" accepts, as things like "^A B" for exemple
will not work. But things like "A B..C D E F.. ..G H...I" should
work as expected.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>