tests/test-dirstate-race.t

clfilter: fallback to unfiltered version when linkrev point to filtered history


On `filectx`, linkrev may point to any revision in the repository. When the
repository is filtered this may lead to `filectx` trying to build `changectx`
for filtered revision. In such case we fallback to creating `changectx` on the
unfiltered version of the reposition. This fallback should not be an issue
because `changectx` from `filectx` are not used in complex operation that
care about filtering. It is complicated to work around the issue in a
clearer way as code raising such `filectx` rarely have access to the
repository directly.

Linkrevs create a lot of issue with filtering. It is stored in revlog entry at
creation time and never changed. Nothing prevent the changeset revision pointed
to become filtered. Several bogus behavior emerge from such situation. Those
bugs are complex to solve and not part of the current effort to install
filtering. This changeset is simple hack that prevent plain crash in favor on
minor misbehavior without visible effect.

This "hack" is longly documented in to code itself to help people that would
look at it in the future.

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m test

Do we ever miss a sub-second change?:

  $ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  >     hg co -qC 0
  >     echo b > a
  >     hg st
  > done
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a