tests/test-merge8.t

test: rename 'test-push-r.t' to 'test-push.t'

We do not have a simple test for 'hg push' but we have multiple tiny tests for
various aspect of it. We'll unify them into a single file, and we start with
'test-push-r.t'. The code is unchanged but we renamed the repository used to
avoid collision with other tests we'll import in coming changesets.

Test timing for the record:

start   end     cuser   csys    real      Test
  1.850   2.640   0.650   0.090   0.790   test-push-validation.t
  2.640   3.520   0.760   0.090   0.880   test-push-hook-lock.t
  0.000   1.850   1.560   0.210   1.850   test-push-r.t

Test for changeset ba7c74081861
(update dirstate correctly for non-branchmerge updates)
  $ hg init a
  $ cd a
  $ echo a > a
  $ hg add a
  $ hg commit -m a
  $ cd ..
  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd a
  $ hg mv a b
  $ hg commit -m move
  $ echo b >> b
  $ hg commit -m b
  $ cd ../b
  $ hg pull ../a
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  (run 'hg update' to get a working copy)
  $ hg update
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cd ..