relnotes/next

commit: clear resolved mergestate even if working copy is clean

If the mergestate has resolved conflicts and a commit is successfully
created (either because there are changes in the working copy or
because ui.allowemptycommit=yes), we will also clear the merge
state. However, if the working copy is clean (and
ui.allowemptycommit=no), we leave the mergestate there. The user may
notice it in `hg resolve -l` output (but not in `hg status -v`
output). It's not clear how the user should clear it, but probably via
`hg co -C .`. It's also quite likely that they won't even notice it
and it will get cleared by a later `hg commit` (of unrelated
changes).

This patch makes it so that `hg commit` also clears resolved merge
conflicts even if the command doesn't end up writing a commit because
the working copy was empty. That's probably a little weird (commands
that abort should generally avoid changing the repo), but it still
seems mostly harmless, and it reduces the risk of more bugs like
https://bz.mercurial-scm.org/show_bug.cgi?id=5494. I just ran into a
version of that bug in the Evolve extension and that's what triggered
this series.

Differential Revision: https://phab.mercurial-scm.org/D8196

== New Features ==

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

 * `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 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.