Re: merge-base: fully contaminate the well.

Linus Torvalds [off-list ref] writes:

Btw, I don't think your contamination logic is necessarily complete. We 
may not even have parsed some of the commits that end up being on that 
strange corner case....

You are right.  And the situation seems really bad.

The full-contaminator is not full at all, and fails miserably in
not so pathlogical case.  If we have something like this:

	1	2	List		A B C D E F G
	F	E	F1 E2		- - - - 2 1 -
        |\     /|	G1 E2 D1 C1	- - 1 1 2 1 1
        \ \   / |	E2 D1 C1	- - 1 1 2 1 1
        |\  D  /|	G3 D3 C3	- - 3 3 2 1 3
        | \ | / |	D3 C3		- - 3 3 2 1 3
        |   C   |	C7		- - 7 3 2 1 3
        |   |   |
        |   B   |
        |   |   /
         \  A  /
          \ | /
            G

we would end up finding D and G and stop there, without ever
seeing A or B.  B _might_ be touched when we look at C at the
last round, but there is no way for us to find G is reachable
from D (or C) without parsing more than what we parsed in the
main loop.

The worst part of this is that you can indefinitely extend C-B-A
chain trivially, and all it takes is the one, initial commit G,
that has a screwed-up timestamp.  All the other commits in this
example are in the right time order.  Very sad.