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copies: fix the changeset based algorithm regarding merge

In 99ebde4fec99, we changed the list of files stored into the `files` field.
This lead to the changeset centric copy algorithm to break in various merge
situation involving merge. Older information could reach the merge through
`p1`, and while information from `p2` was strictly fresher, it would get
overwritten anyway.

We update the situation with more details about which revision introduces rename
information. This help use making the right decision in case of merge.

We are now running a more comprehensive suite of test with include this kind of
situation. The behavior differ slightly from the filelog based in a couple of
instance. There is mostly two distinct cases:

1) there are conflicting rename information in a merge (different rename history
on each side). In this case the filelog based implementation arbitrarily pick a
side based on the file-revision-number. So it depends on a local factor. The
changeset centric algorithm will use a deterministic approach, by picking the
information coming from the first parent of the merge. This is stable across
different clone.

2) rename information related to file that exist in both source and destination.
The filelog based implementation do not even try to detect these, however the
changeset centric one get them for "free" (it is simpler to detect them than
not).

The new implementation focus on correctness. Performance improvement will come
later.

Differential Revision: https://phab.mercurial-scm.org/D8244

== New Features ==

 * `hg purge`/`hg clean` can now delete ignored files instead of
   untracked files, with the new -i flag.

 * `hg pull` now has a `--confirm` flag to prompt before applying changes.
   Config option `pull.confirm` is also added for that.

 * `hg log` now defaults to using an '%' symbol for commits involved
    in unresolved merge conflicts. That includes unresolved conflicts
    caused by e.g. `hg update --merge` and `hg graft`. '@' still takes
    precedence, so what used to be marked '@' still is.

 * New `conflictlocal()` and `conflictother()` revsets return the
   commits that are being merged, when there are conflicts. Also works
   for conflicts caused by e.g. `hg graft`.

 * `hg copy --forget` can be used to unmark a file as copied.

 * The `format.revlog-compression` configuration entry now accept a list. The
   first available option will be used. for example setting::

     [format]
     revlog-compression=zstd, zlib

   Will use `zstd` compression for new repositories is available, and will
   simply fall back to `zlib` if not.

 * `hg debugmergestate` output is now templated, which may be useful
   e.g. for IDEs that want to help the user resolve merge conflicts.


== New Experimental Features ==

 * `hg copy` now supports a `--at-rev` argument to mark files as
   copied in the specified commit. It only works with `--after` for
   now (i.e., it's only useful for marking files copied using non-hg
   `cp` as copied).

 * Use `hg copy --forget --at-rev REV` to unmark already committed
   copies.

== Bug Fixes  ==

 * Fix server exception when concurrent pushes delete the same bookmark

 * Prevent pushes of divergent bookmarks (foo@remote)

 * The push error "remote repository changed while pushing - please
   try again" now only happens when a concurrent push changed related
   heads (instead of when a concurrent pushed any revision).


== Backwards Compatibility Changes ==

 * When `hg rebase` pauses for merge conflict resolution, the working
   copy will no longer have the rebased node as a second parent. You
   can use the new `conflictparents()` revset for finding the other
   parent during a conflict.

 * `hg rebase` now accepts repeated `--source` and `--base`
   arguments. For example, `hg rebase --source 'A + B'` is equivalent
   to `hg rebase --source A --source B`. This is a
   backwards-incompatible change because it will break overriding an
   alias `myrebase = rebase --source A` by `hg myrebase --source B`
   (it will now rebase `(A + B)::` instead of `B::`).

 * `hg recover` does not verify the validity of the whole repository
   anymore. You can pass `--verify` or call `hg verify` if necessary.

 * `hg debugmergestate` output format changed. Let us know if that is
   causing you problems and we'll roll it back.

 * Resolved merge conflicts are now cleared by `hg commit` even if the
   working copy has no changes.


== Internal API Changes ==

 * The deprecated `ui.progress()` has now been deleted. Please use
   `ui.makeprogress()` instead.

 * `hg.merge()` now takes a `ctx` instead of the previous `repo` and
   `node` arguments.

 * `hg.merge()` has lost its `abort` argument. Please call
   `hg.abortmerge()` directly instead.

 * `hg.merge()` has lost its `mergeforce` argument. It should have
   only ever been called with the same value as the `force` argument.

 * The `*others` argument of `cmdutil.check_incompatible_arguments()`
   changed from being varargs argument to being a single collection.