tests/test-push-checkheads-superceed-A1.t

delta-find: split the "sparse" part of `_pre_filter_rev` in a method

Since `_pre_filter_rev` contains logic from various sources of constraint, we
start splitting is in subfunction to clarify and document the grouping.

====================================
Testing head checking code: Case A-1
====================================

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Category A: simple case involving a branch being superseded by another.
TestCase 1: single-changeset branch

.. old-state:
..
.. * 1 changeset branch
..
.. new-state:
..
.. * 1 changeset branch succeeding to A
..
.. expected-result:
..
.. * push allowed
..
.. graph-summary:
..
..   A ø⇠◔ A'
..     |/
..     ●

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

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

  $ mkdir A1
  $ cd A1
  $ setuprepos
  creating basic server and client repo
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd client
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A1
  created new head
  $ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
  1 new obsolescence markers
  obsoleted 1 changesets
  $ hg log -G --hidden
  @  f6082bc4ffef (draft): A1
  |
  | x  8aaa48160adc (draft): A0
  |/
  o  1e4be0697311 (public): root
  

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

  $ hg push
  pushing to $TESTTMP/A1/server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  1 new obsolescence markers
  obsoleted 1 changesets

  $ cd ../..