context: avoid using a context object as a changeid I find it misleading to pass changeid=changectx. It currently works to do that because there's weird (IMO) handling of it in basectx.__new__. I'm planning on removing that code. Passing changeid as "changeid" and context as "context" makes it more readable. Note that the documentation of filectx.__init__ doesn't even seem to be aware that a changeid can be a context ("changeset revision, node, or tag"). Differential Revision: https://phab.mercurial-scm.org/D2967

context: remove unwanted assignments in basectx.__new__() (API) The two subclasses in core apparently didn't trust __new__() to do the job anyway (they both reassigned all the properties after). Differential Revision: https://phab.mercurial-scm.org/D2966

streamclonebundle: make sure we accept new stream clone bundle spec When asked specifically, the code do a sanity check on the clone bundle to ensure it's a stream bundle. As we introduced a new stream bundle spec, update the logic to support it. With this final changeset, we can now announce safely a stream v2 clone bundle and old clients would not crash trying to process it. This changeset address the last comment from Gregory Szorc on the stream v2 bundle series. Differential Revision: https://phab.mercurial-scm.org/D1957

streamclonebundle: add a test for stream clone bundle v2 Differential Revision: https://phab.mercurial-scm.org/D1956

bundlespec: add support for some variants This way the stream v2 bundle spec can disable the changegroup part while enabling the stream v2 part. Differential Revision: https://phab.mercurial-scm.org/D1955

bundle: add the possibility to bundle a stream v2 part Differential Revision: https://phab.mercurial-scm.org/D1954

streambundlev2: add a new test-file Add the new test file in a separate changeset before supporting the new format so we better see the differences. Differential Revision: https://phab.mercurial-scm.org/D1953

bundlespec: move computing the bundle contentops in parsebundlespec We will introduce a new bundlespec for stream bundle which will influence the contentops. Differential Revision: https://phab.mercurial-scm.org/D1952

bundlespec: introduce an attr-based class for bundlespec We will add support of contentops in the next patch, introduce a class instead of returning a 4-items tuple. Differential Revision: https://phab.mercurial-scm.org/D2971

templater: factor out unwrapastype() from evalastype() So ParseError of unwrapastype() can be caught reliably.