D4789: narrow: check for servers' narrow support before doing anything (BC)

[pulkit (Pulkit Goyal)]

pulkit added a comment.


  In https://phab.mercurial-scm.org/D4789#72717, @martinvonz wrote:
  
  > > This is BC because new clients won't be able to extend from old narrow-enabled servers.
  >
  > I think your previous patch was also BC in that sense since it started requiring the server to have the ellipses wire capability when widening with ellipsis nodes. It's not a problem for us to add that capability (we already have), but you may want to mention it there for consistency :), if I understood that right.
  
  
  I am not whether that patch stands as a BC but yes, the whole rework and refactoring during this cycle make big BC's in how narrow extension work and I doubt that a client with hg-4.8 will be able to use narrow with server which is at hg-4.7.

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REVISION DETAIL
  https://phab.mercurial-scm.org/D4789

To: pulkit, durin42, #hg-reviewers
Cc: martinvonz, mercurial-devel