tests/test-push-checkheads-pruned-B8.t

simplemerge: stop merging file flags

As 384df4db6520 (merge: merge file flags together with file content,
2013-01-09) explains, we shouldn't do a 3-way merge of the
symlink. However, since 84614212ae39 (flags: actually merge flags in
simplemerge, 2020-05-16), we do that in
`simplemerge.simplemerge()`. What's more, the merging of the
executable flag there isn't actually necessary; it was made a no-op by
the very next commit, i.e. 4234c9af515d (flags: read flag from
dirstate/disk for workingcopyctx (issue5743), 2020-05-16).

I found the overall flag-merging code (not the bit in
`simplemerge.py`) very hard to follow, but I think I now finally
understand how it works. `mergestate.resolve()` calculates the merged
file flags and sets them on the local side of the merge (confusingly
by calling `_restore_backup()`). Then it calls
`filemerge.filemerge()`, which in turn calls
`simplemerge.simplemerge()` (if premerge is enabled). That means that
the flags on the local side `fcs.flags()` are already correct when the
flag-merging code in `simplemerge.simplemerge()` runs. Interestingly,
that code still works when the local side already has the merged
value, it just doesn't change the value. Here's a truth table to
explain why:

```
BLOMCAR
0000000
0011111
0101011
0111111
1000000
1010000
1100000
1111101
```

B: Base
L: Local
O: Other
M: Merged flags from `mergestate.resolve()`, i.e. what's called "local"
   when we get to `simplemerge.simplemerge()`
C: `commonflags` in `simplemerge.simplemerge()`, i.e. `M & O`
A: `addedflags` in `simplemerge.simplemerge()`, i.e. `(M ^ O) - B`
R: Re-merged flags `simplemerge.simplemerge()`, i.e. `C | A`

As you can see, the re-merged flags are always unchanged compared to
the initial merged flags (R equals M).

Therefore, this patch effectively backs out 84614212ae39. (I might
later refactor this code to have the flags explicitly passed in.)

`simplemerge.simplemerge()` is also called from
`contrib/simplemerge.py`, but that code never passes any flags.

Differential Revision: https://phab.mercurial-scm.org/D11879

====================================
Testing head checking code: Case B-2
====================================

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 B: simple case involving pruned changesets
TestCase 2: multi-changeset branch, head is pruned, rest is superceeded, through other

.. old-state:
..
.. * 2 changeset branch
..
.. new-state:
..
.. * old head is rewritten then pruned
.. * 1 new branch succeeding to the other changeset in the old branch (through another obsolete branch)
..
.. expected-result:
..
.. * push allowed
..
.. graph-summary:
..
..   B ø⇠⊗ B'
..     | | A'
..   A ø⇠ø⇠◔ A''
..     |/ /
..     | /
..     |/
..     ●

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

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

  $ mkdir B8
  $ cd B8
  $ 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/B8/server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets d73caddc5533 (1 drafts)
  (run 'hg update' to get a working copy)
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkcommit A1
  created new head
  $ mkcommit B1
  $ hg up 0
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ mkcommit A2
  created new head
  $ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
  1 new obsolescence markers
  obsoleted 1 changesets
  1 new orphan changesets
  $ hg debugobsolete `getid "desc(B0)" ` `getid "desc(B1)"`
  1 new obsolescence markers
  obsoleted 1 changesets
  $ hg debugobsolete --record-parents `getid "desc(B1)"`
  1 new obsolescence markers
  obsoleted 1 changesets
  $ hg debugobsolete `getid "desc(A1)" ` `getid "desc(A2)"`
  1 new obsolescence markers
  obsoleted 1 changesets
  $ hg log -G --hidden
  @  c1f8d089020f (draft): A2
  |
  | x  262c8c798096 (draft): B1
  | |
  | x  f6082bc4ffef (draft): A1
  |/
  | x  d73caddc5533 (draft): B0
  | |
  | x  8aaa48160adc (draft): A0
  |/
  o  1e4be0697311 (public): root
  

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

  $ hg push
  pushing to $TESTTMP/B8/server
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  4 new obsolescence markers
  obsoleted 2 changesets

  $ cd ../..