tests/test-exchange-obsmarkers-case-C4.t

convert: don't drop commits that are empty in the source when using --filemap

I ran into this when using `hg lfconvert --to-normal` (which uses the filemap
class internally), and saw that commits with nothing but a branch change were
dropped.  We could put in an option that only lfconvert uses internally.  But
silently dropping anything other than a commit where all changes were excluded
seems unintended.  For example, there's a message in mercurial_sink.putcommit()
if it drops an empty commit.  (And the reason that isn't kicking in here is
because lfconvert isn't passing --filemap, so the self.filemapmode conditional
there is always False.)

The naive change of `return not files` broke test-convert-filemap.t, so this is
a little more elaborate than needed for converting from largefiles.

============================================
Testing obsolescence markers push: Cases C.4
============================================

Mercurial pushes obsolescences markers relevant to the "pushed-set", the set of
all changesets that requested to be "in sync" after the push (even if they are
already on both side).

This test belongs to a series of tests checking such set is properly computed
and applied. This does not tests "obsmarkers" discovery capabilities.

Category C: advanced case
TestCase 4: multiple successors, one is pruned

C.4 multiple successors, one is pruned
======================================

.. (A similarish situation can appends with split markers see the Z section)
..
.. {{{
..        A
..    B ○⇢ø⇠⊗ C
..       \|/
..        ● O
.. }}}
..
.. Marker exist from:
..
..  * `A ø⇠○ B`
..  * `A ø⇠○ C`
..  * C (prune)
..
.. Command run:
..
..  * hg push -r O
..
.. Expected exchange:
..
..  * `A ø⇠○ C`
..  * C (prune)
..
.. Expected exclude:
..
..  * `A ø⇠○ B`

Setup
-----

  $ . $TESTDIR/testlib/exchange-obsmarker-util.sh

Implemented as the non-split version

  $ setuprepos C.4
  creating test repo for test case C.4
  - pulldest
  - main
  - pushdest
  cd into `main` and proceed with env setup
  $ cd main
  $ mkcommit A
  $ hg update -q 0
  $ mkcommit B
  created new head
  $ hg update -q 0
  $ mkcommit C
  created new head
  $ hg debugobsolete --hidden `getid 'desc(A)'` `getid 'desc(B)'`
  obsoleted 1 changesets
  $ hg debugobsolete --hidden `getid 'desc(A)'` `getid 'desc(C)'`
  2 new content-divergent changesets
  $ hg prune -qd '0 0' .
  $ hg log -G --hidden
  x  7f7f229b13a6 (draft): C
  |
  | o  35b183996678 (draft): B
  |/
  | x  f5bc6836db60 (draft): A
  |/
  @  a9bdc8b26820 (public): O
  
  $ inspect_obsmarkers
  obsstore content
  ================
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  $ cd ..
  $ cd ..

Actual Test
-----------

  $ dotest C.4 O
  ## Running testcase C.4
  # testing echange of "O" (a9bdc8b26820)
  ## initial state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  # obstore: pulldest
  ## pushing "O" from main to pushdest
  pushing to pushdest
  searching for changes
  no changes found
  remote: 2 new obsolescence markers
  ## post push state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  ## pulling "a9bdc8b26820" from main into pulldest
  pulling from main
  no changes found
  2 new obsolescence markers
  ## post pull state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}