On Tue, 18 Nov 2014, Jonathan Nieder wrote:
> Alan Stern wrote:
>
> > Tracking down regressions. Bisection isn't perfect. Suppose a
> > bisection run ends up saying that B is the first bad commit. It's easy
> > enough to build B and test it, to verify that it really is bad.
> >
> > But to be sure that B introduced the fault, it would help to find the
> > latest commit that doesn't include B's changes -- that is, the latest
> > commit that B isn't reachable from (or the maximal elements in the set
> > of all such commits).
>
> Isn't that B^ (or B^ and B^2, if B is a merge)?
No. Here's a simple example:
Y
/
/
X--B
In this diagram, X = B^. But B isn't reachable from either X or Y,
whereas it is reachable from one of X's children (namely Y). Therefore
Y is the unique maximal commit which B is not reachable from.
Alan Stern
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