bundlerepo: move temp bundle creation to a separate function A future patch will refactor certain parts of bundlerepo initiatlization such that we need to create temp bundles from another function. Let's move this to another function to support that. Differential Revision: https://phab.mercurial-scm.org/D288

exchange: don't attempt phase exchange if phase-heads was in bundle The Mercurial core server doesn't yet include phase-heads parts in the bundle, but our Google-internal server wants to do that. Unfortunately, the usual exchange still happens even if phase-heads part is included (including the short-circuited one for old/publishing servers). That means that even if our server (again, the Google-internal one, but also future Mercurial core servers) includes a phase-heads part to indicate that some heads should be drafts, that would still get overwritten by the phase updating that happens after. So let's fix that by marking the phase step done if we receive at least one phase-heads part in the bundle. Differential Revision: https://phab.mercurial-scm.org/D440

pushvars: do not mangle repo state Setting `repo._shellvars` works but is not a clean way to pass the pushvars information from the push command to the exchange operation. Therefore change it to actually pass `pushvars` as a push operation argument instead. This makes third party extension like remotenames easier to support pushvars cleanly. The key value parsing and verification code has been moved to a lower level so it's harder to be bypassed and easier to be used in remotenames which could replace `push` command entirely. Differential Revision: https://phab.mercurial-scm.org/D423