D6887: upgrade: detect the side-data format variants

[marmoute (Pierre-Yves David)]

marmoute added inline comments.

INLINE COMMENTS

> durin42 wrote in test-lfs-serve.t:136
> how about:
> 
> "Allows storage of extra data alongside a revision."

This looks good to me. Updating shortly.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D6887/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D6887

To: marmoute, durin42, #hg-reviewers
Cc: mjpieters, mercurial-devel