setup: register zope.interface packages and compile C extension With this change, we should be able to use zope.interface in core! Differential Revision: https://phab.mercurial-scm.org/D2932

thirdparty: allow zope.interface.advice to be lazily imported The symbol from this module is only used in functions. Let's access that symbol through its imported module so importing zope.interface.advice can be lazy. Differential Revision: https://phab.mercurial-scm.org/D2931

thirdparty: port zope.interface to relative imports By using relative imports, we're guaranteed to get modules vendored with Mercurial rather than other random modules that might be in sys.path. My editor strips trailing whitespace on save. So some minor source code cleanup was also performed as part of this commit. # no-check-commit because some modified lines have double newlines Differential Revision: https://phab.mercurial-scm.org/D2930

thirdparty: don't make zope a namespace package There are a gazillion zope.* packages in the wild. So zope/__init__.py needs to be a namespace package. But in Mercurial, we have 1 zope package. And even if we had multiple packages, they'd all be in thirdparty/zope/. So we don't need a namespace package. Differential Revision: https://phab.mercurial-scm.org/D2929

thirdparty: vendor zope.interface 4.4.3 I've been trying to formalize interfaces for various components of Mercurial. So far, we've been using the "abc" package. This package is "good enough" for a lot of tasks. But it quickly falls over. For example, if you declare an @abc.abstractproperty, you must implement that attribute with a @property or the class compile time checking performed by abc will complain. This often forces you to implement dumb @property wrappers to return a _ prefixed attribute of the sane name. That's ugly. I've also wanted to implement automated checking that classes conform to various interfaces and don't expose other "public" attributes. After doing a bit of research and asking around, the general consensus seems to be that zope.interface is the best package for doing interface-based programming in Python. It has built-in support for verifying classes and objects conform to interfaces. It allows an interface's properties to be defined during __init__. There's even an "adapter registry" that allow you to register interfaces and look up which classes implement them. That could potentially be useful for places where our custom registry.py modules currently facilitates central registrations, but at a type level. Imagine extensions providing alternate implementations of things like the local repository interface to allow opening repositories with custom requirements. Anyway, this commit vendors zope.interface 4.4.3. The contents of the source tarball have been copied into mercurial/thirdparty/zope/ without modifications. Test modules have been removed because they are not interesting to us. The LICENSE.txt file has been copied so it lives next to the source. The Python modules don't use relative imports. zope/__init__.py defines a namespace package. So we'll need to modify the source code before this package is usable inside Mercurial. This will be done in subsequent commits. # no-check-commit for various style failures Differential Revision: https://phab.mercurial-scm.org/D2928

context: set repo property in basectx It seems like a good practice to call the super constructor. Let's start by passing the repo along to basectx so it can assign it to a private attribute. We should perhaps pass the rev and node along as well, but that requires more work before it can be done. Differential Revision: https://phab.mercurial-scm.org/D2970

context: move reuse of context object to repo.__getitem__ (API) As an example of how weird the basectx.__new__ is: whenever you create a workingctx, basectx.__new__ gets called first. Since our __new__ has a "changeid" argument as second parameter, when create the workingctx(repo, text="blah"), the text gets bound to "changeid". Since a string isn't a basectx, our __new__ ends up not doing anything funny, but that's still very confusing code. Another case is metadataonlyctx.__new__(), which I think exists in order to prevent metadataonlyctx.__init__'s third argument (originalctx) from being interpreted as a changeid in basectx.__new__(), thereby getting reused. Let's move this to repo.__getitem__ instead, where it will be pretty obvious what the code does. After this patch, changectx(ctx) will be an error (it will fail when trying to see if it's a 20-byte string). Differential Revision: https://phab.mercurial-scm.org/D2969