D4099: narrow: move .hg/narrowspec to .hg/store/narrowspec (BC)

durin42 (Augie Fackler) phabricator at mercurial-scm.org
Tue Aug 7 10:32:17 EDT 2018


durin42 added a comment.


  In https://phab.mercurial-scm.org/D4099#64268, @pulkit wrote:
  
  > In https://phab.mercurial-scm.org/D4099#64266, @durin42 wrote:
  >
  > > There are non-Google users of narrow at this point (recall we've gotten non-Googler patches), so please publish the temporary migration hack someplace for the benefit of the other users.
  > >
  > > (A phabricator review that we immediately abandon would probably be fine, but we should definitely make a note in the relnotes for 4.8)
  >
  >
  > Yes, we might roll-out narrow with mercurial 4.7 first, so this script will be of great help. (BTW, isn't it just a move of file?)
  
  
  It's "just" a move, but typically the way we handle these migrations at Google is we write an extension that does one of the following:
  
  1. Hijacks reads for the new file and reads the old file
  2. Hijacks reads for the new file if it doesn't exist and moves the new file
  
  we run in mode 1 when we're doing the rollout and might roll back, then switch to mode 2 when we're past the rubicon on the rollout and can finalize the data migration. Once everyone has run the extension in mode 2 for a while, we reap the extension.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4099

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


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