CONTRIBUTING

strip: include phases in bundle (BC)

Before this patch, unbundling a stripped changeset would make it a
draft (unless the parent was secret). This meant that one would lose
phase information when stripping and unbundling secret changesets. The
same thing was true for public changesets. While stripping public
changesets is generally rare, it's done frequently by e.g. the
narrowhg extension.

We also include the phases in the temporary bundle, just in case
stripping were to fail after that point, so the user can still restore
the repo including phase information. Before this patch, the phases
were left untouched during the bundling and unbundling of the
temporary bundle. Only at the end of the transaction would
phasecache.filterunknown() be called to remove phase roots that were
no longer valid. We now need to call that also after the first
stripping, i.e. before applying the temporary bundle. Otherwise
unbundling the temporary bundle will cause a read of the phase cache
which has stripped changesets in the cache and that fails.

Like with obsmarkers, we unconditionally include the phases in the
bundle when stripping (when using bundle2, such as when generaldelta
is enabled). The reason for doing that for strip but not for bundle is
that strip bundles are not meant to be shared outside the repo, so we
don't care as much about compatibility.

Our full contribution guidelines are in our wiki, please see:

https://www.mercurial-scm.org/wiki/ContributingChanges

If you just want a checklist to follow, you can go straight to

https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist

If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).