Re: [PATCH v3] doc-diff: don't `cd_to_toplevel`

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Even when there are even only as much as 12 merge bases to test (which is
> the current number of merge bases between `next` and `pu`),...
> ...
> And I sadly have to report that that's not the end of it. Back when I
> implemented the automatic bisect after failed builds (for details, see
> https://github.com/git-for-windows/build-extra/commit/c7e01e82c), I had to
> turn it off real quickly because the dumb bisect between `next` and `pu`
> regularly ran into the 4h timeout.

Would it make it easier for you if you substituted all the mention
of 'next' in your message with 'pu^{/^### match next}'?  

That mid-point between 'master' and 'pu' is designed to contain
exactly the same set of non-merge commits 'next' has, with the tree
that is identical to that of 'next', and from there to the tip of
'pu' forms a single strand of merges of tips of topic branches that
are not yet merged to 'next' (by definition, it itself is the merge
base of it and 'pu').

Bisecting along the first-parent chain from there to the tip of 'pu'
would let us identify which merge is faulty as the first-and-quick
pass and currently there are about 20 merges in that range on the
first-parent chain.