tests/test-merge10.t

obsolescence: add test case B-4 for obsolescence markers exchange

About 3 years ago, in August 2014, the logic to select what markers to select on
push was ported from the evolve extension to Mercurial core. However, for some
unclear reasons, the tests for that logic were not ported alongside.
I realised it a couple of weeks ago while working on another push related issue.
I've made a clean up pass on the tests and they are now ready to integrate the
core test suite. This series of changesets do not change any logic. I just adds
test for logic that has been around for about 10 versions of Mercurial.

They are a patch for each test case. It makes it easier to review and postpone
one with documentation issues without rejecting the wholes series.

This patch introduce case B4: Pruned changeset on common part of history

Each test case comes it in own test file. It help parallelism and does not
introduce a significant overhead from having a single unified giant test file.
Here are timing  to support this claim.

# Multiple test files version:
# run-tests.py --local -j 1 test-exchange-*.t
53.40s user 6.82s system 85% cpu 1:10.76 total
52.79s user 6.97s system 85% cpu 1:09.97 total
52.94s user 6.82s system 85% cpu 1:09.69 total

# Single test file version:
# run-tests.py --local -j 1 test-exchange-obsmarkers.t
52.97s user 6.85s system 85% cpu 1:10.10 total
52.64s user 6.79s system 85% cpu 1:09.63 total
53.70s user 7.00s system 85% cpu 1:11.17 total

Test for changeset 9fe267f77f56ff127cf7e65dc15dd9de71ce8ceb
(merge correctly when all the files in a directory are moved
but then local changes are added in the same directory)

  $ hg init a
  $ cd a
  $ mkdir -p testdir
  $ echo a > testdir/a
  $ hg add testdir/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
  $ echo alpha > testdir/a
  $ hg commit -m remote-change
  $ cd ..

  $ cd b
  $ mkdir testdir/subdir
  $ hg mv testdir/a testdir/subdir/a
  $ hg commit -m move
  $ mkdir newdir
  $ echo beta > newdir/beta
  $ hg add newdir/beta
  $ hg commit -m local-addition
  $ hg pull ../a
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up -C 2
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge
  merging testdir/subdir/a and testdir/a to testdir/subdir/a
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg stat
  M testdir/subdir/a
  $ hg diff --nodates
  diff -r bc21c9773bfa testdir/subdir/a
  --- a/testdir/subdir/a
  +++ b/testdir/subdir/a
  @@ -1,1 +1,1 @@
  -a
  +alpha

  $ cd ..