[PATCH STABLE] revlog: make sure we never use sparserevlog without general delta (issue6056)

[Yuya Nishihara]

On Tue, 29 Jan 2019 10:41:17 -0800, Gregory Szorc wrote:
> On Tue, Jan 29, 2019 at 3:44 AM Yuya Nishihara <yuya at tcha.org> wrote:
> > is a global requirement. I don't know if sparserevlog should be a revlog
> > flag
> > or not, but anyway only thing we can do here is to turn off the sparse, as
> > your
> > patch does.
> >
> 
> Sparse should have a revlog flag in addition to a repo requirement. My
> understanding is we already shipped sparse support in 4.8. This means we
> can't introduce a revlog flag (and corresponding repo requirement) without
> a BC change. I started a series to introduce revlog version 2 (mainly to
> support zstd compression in revlogs). We can do things more properly in
> revlog version 2. But I fear the lack of a sparse revlog flag will just
> have to be an historical wart since we've already shipped it.

Maybe we should document the wart in revlog.py so we won't make the same
kind of mistakes in future?