git-bisect is magical

[walt <wa1ter@myrealbox.com>]

Arthur C. Clarke's Third Law states:  Any sufficiently advanced
technology is indistinguishable from magic.

You guys have done it -- I can't distinguish git-bisect from
magic.  It's wonderful, and thank you!

I used it for the first time this morning to find the commit
which caused some kernel breakage.  I just sent off an email
to the developer whose commit did the breakage, and it only
took me about 45 minutes.  (Now all I need to do is sit back
and wait for his reply saying 'You're an idiot!')

I have one minor suggestion for howto/isolate-bugs-with-bisect.
Linus states:
       git bisect good ORIG_HEAD       <- mark ORIG_HEAD as good (or
                                           whatever other known-good
                                           thing you booted last)

Well, in my case, I new the last good kernel was *two* updates ago,
so ORIG_HEAD wasn't the right thing to use.  I had to guess what
to type instead of 'ORIG_HEAD'.

Which leads to one more question:  I have my kernel configured to
add the -gxxxxxxxx localversion string to the kernel name.  I took
a wild guess that the xxxxxxxx was the right thing to substitute
for 'ORIG_HEAD' and I got lucky.  But what about someone who
doesn't know the magic 'xxxxxxxx' to use?  If I didn't know enough
to keep a week's worth of daily kernel-builds with the 'xxxxxxxx'
to guide me, would I still be able to do what I did today?
(For example, if this had been a 'git' bug instead of a kernel bug,
I don't think I could have figured out how to use git-bisect to find
the bug -- could I?)

Thanks!