tr-summary: keep a weakref to the unfiltered repository
Repoview can have a different life cycle, causing issue in some corner
cases. The particular instance that revealed this comes from localpeer. The
localpeer hold a reference to the unfiltered repository, but calling 'local()'
will create an on-demand 'visible' repoview. That repoview can be garbaged
collected any time. Here is a simplified step by step reproduction::
1) tr = peer.local().transaction('foo')
2) tr.close()
After (1), the repoview object is garbage collected, so weakref used in (2)
point to nothing.
Thanks to Sean Farley for helping raising and debugging this issue.
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https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
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commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).