tests/test-sparse-fsmonitor.t

localrepo: stop doing special dirstate backup at transaction open

Since the dirstate writes are already managed by the transaction, we already do
a backup of the dirstate when necessary (and even trigger one to keep `hg
rollback` happy).

We needs some special code to deal with the initial empty checkout, but it is
not too complicated.

Managing variable filename (as dirstate-v2 uses) at the "journalfile" level, is
complex and fragile (which is consistent with the fact these files are not
journal…). If we no longer do it, our life is significantly simpler.

In some sense, we apply the xkcd-1134¹ solution to our savebackup/restorebackup
problem.

[1] https://xkcd.com/1134/

(the change to test-hardlink are expect as decreasing the number of duplicated
backup drive the hardlink count down)

This test doesn't yet work due to the way fsmonitor is integrated with test runner

  $ exit 80

test sparse interaction with other extensions

  $ hg init myrepo
  $ cd myrepo
  $ cat > .hg/hgrc <<EOF
  > [extensions]
  > sparse=
  > strip=
  > EOF

Test fsmonitor integration (if available)
TODO: make fully isolated integration test a'la https://github.com/facebook/watchman/blob/master/tests/integration/WatchmanInstance.py
(this one is using the systemwide watchman instance)

  $ touch .watchmanconfig
  $ echo "ignoredir1/" >> .hgignore
  $ hg commit -Am ignoredir1
  adding .hgignore
  $ echo "ignoredir2/" >> .hgignore
  $ hg commit -m ignoredir2

  $ hg sparse --reset
  $ hg sparse -I ignoredir1 -I ignoredir2 -I dir1

  $ mkdir ignoredir1 ignoredir2 dir1
  $ touch ignoredir1/file ignoredir2/file dir1/file

Run status twice to compensate for a condition in fsmonitor where it will check
ignored files the second time it runs, regardless of previous state (ask @sid0)
  $ hg status --config extensions.fsmonitor=
  ? dir1/file
  $ hg status --config extensions.fsmonitor=
  ? dir1/file

Test that fsmonitor ignore hash check updates when .hgignore changes

  $ hg up -q ".^"
  $ hg status --config extensions.fsmonitor=
  ? dir1/file
  ? ignoredir2/file