dirstate: add a way to test races happening during status
We add the `devel.sync.status.pre-dirstate-write-file` config option to easily
test what happens when other operations happen during the window where
`hg status` is done working but has not updated the cache on disk yet.
We introduce the framework for testing such races too, actual tests will be
added in the next changesets. For now the test is only checking dirstate-v1. We
will extend the test coverage later too.
Check test documentation for details.
Code change from Raphaël Gomès <rgomes@octobus.net>
Test change from Pierre-Yves David <pierre-yves.david@octobus.net>
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true