tests/test-push-checkheads-partial-C4.t

wireproto: support for receiving multiple requests

Now that we have request IDs on each frame and a specification
that allows multiple requests to be issued simultaneously,
possibly interleaved, let's teach the server to deal with that.

Instead of tracking the state for *the* active command request,
we instead track the state of each receiving command by its
request ID. The multiple states in our state machine for processing
each command's state has been collapsed into a single state for
"receiving commands."

Tests have been added so our branch coverage covers all meaningful
branches.

However, we did lose some logical coverage. The implementation
of this new feature opens up the door to a server having partial
command requests when end of input is reached. We will probably
want a mechanism to deal with partial requests. For now, I've
tracked that as a known issue in the class docstring. I've
also noted an abuse vector that becomes a little bit easier to
exploit with this feature.

Differential Revision: https://phab.mercurial-scm.org/D2870

====================================
Testing head checking code: Case C-4
====================================

Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.

This case is part of a series of tests checking this behavior.

Category C: case were the branch is only partially obsoleted
TestCase 4: 2 changeset branch, only the base is pruned

.. old-state:
..
.. * 2 changeset branch
..
.. new-state:
..
.. * old base is pruned
.. * 1 new unrelated branch
..
.. expected-result:
..
.. * push denied
..
.. graph-summary:
..
..   B ◔
..     |
..   A ⊗ ◔ C
..     |/
..     ●

  $ . $TESTDIR/testlib/push-checkheads-util.sh

Test setup
----------

  $ mkdir C4
  $ cd C4
  $ setuprepos
  creating basic server and client repo
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd server
  $ mkcommit B0
  $ cd ../client
  $ hg pull
  pulling from $TESTTMP/C4/server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets d73caddc5533
  (run 'hg update' to get a working copy)
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit C0
  created new head
  $ hg debugobsolete --record-parents `getid "desc(A0)"`
  obsoleted 1 changesets
  1 new orphan changesets
  $ hg log -G --hidden
  @  0f88766e02d6 (draft): C0
  |
  | *  d73caddc5533 (draft): B0
  | |
  | x  8aaa48160adc (draft): A0
  |/
  o  1e4be0697311 (public): root
  

Actual testing
--------------

  $ hg push --rev 'desc(C0)'
  pushing to $TESTTMP/C4/server
  searching for changes
  abort: push creates new remote head 0f88766e02d6!
  (merge or see 'hg help push' for details about pushing new heads)
  [255]

  $ cd ../..