relnotes: copy "next" to "5.5" and clear "next"

The same procedure as every year^Wcycle.

Differential Revision: https://phab.mercurial-scm.org/D8839

relnotes/next

 == New Features ==
 
- * clonebundles can be annotated with the expected memory requirements
-   using the `REQUIREDRAM` option. This allows clients to skip
-   bundles created with large zstd windows and fallback to larger, but
-   less demanding bundles.
-
- * The `phabricator` extension now provides more functionality of the
-   arcanist CLI like changing the status of a differential.
-
- * Phases processing is much faster, especially for repositories with
-   old non-public changesets.
 
 
 == New Experimental Features ==
 
@@ -13,17 +3,8 @@
 
 
 == New Experimental Features ==
 
- * The core of some hg operations have been (and are being)
-   implemented in rust, for speed. `hg status` on a repository with
-   300k tracked files goes from 1.8s to 0.6s for instance.
-   This has currently been tested only on linux, and does not build on
-   windows. See rust/README.rst in the mercurial repository for
-   instructions to opt into this.
-
- * An experimental config `rewrite.empty-successor` was introduced to control
-   what happens when rewrite operations result in empty changesets.
 
 
 == Bug Fixes ==
 
@@ -26,25 +7,8 @@
 
 
 == Bug Fixes ==
 
- * For the case when connected to a TTY, stdout was fixed to be line-buffered
-   on Python 3 (where it was block-buffered before, causing the process to seem
-   hanging) and Windows on Python 2 (where it was unbuffered before).
-
- * Subversion sources of the convert extension were fixed to work on Python 3.
-
- * Subversion sources of the convert extension now interpret the encoding of
-   URLs like Subversion. Previously, there were situations where the convert
-   extension recognized a repository as present but Subversion did not, and
-   vice versa.
-
- * The empty changeset check of in-memory rebases was fixed to match that of
-   normal rebases (and that of the commit command).
-
- * The push command now checks the correct set of outgoing changesets for
-   obsolete and unstable changesets. Previously, it could happen that the check
-   prevented pushing changesets which were already on the server.
 
 
 == Backwards Compatibility Changes ==
 
@@ -47,20 +11,8 @@
 
 
 == Backwards Compatibility Changes ==
 
- * Mercurial now requires at least Python 2.7.9 or a Python version that
-   backported modern SSL/TLS features (as defined in PEP 466), and that Python
-   was compiled against a OpenSSL version supporting TLS 1.1 or TLS 1.2
-   (likely this requires the OpenSSL version to be at least 1.0.1).
- 
- * The `hg perfwrite` command from contrib/perf.py was made more flexible and
-   changed its default behavior. To get the previous behavior, run `hg perfwrite
-   --nlines=100000 --nitems=1 --item='Testing write performance' --batch-line`.
-
- * The absorb extension now preserves changesets with no file changes that can
-   be created by the commit command (those which change the branch name
-   compared to the parent and those closing a branch head).
 
 
 == Internal API Changes ==
 
@@ -63,18 +15,4 @@
 
 
 == Internal API Changes ==
 
- * logcmdutil.diffordiffstat() now takes contexts instead of nodes.
-
- * The `mergestate` class along with some related methods and constants have
-   moved from `mercurial.merge` to a new `mercurial.mergestate` module.
-
- * The `phasecache` class now uses sparse dictionaries for the phase data.
-   New accessors are provided to detect if any non-public changeset exists
-   (`hasnonpublicphases`) and get the correponsponding root set
-   (`nonpublicphaseroots`).
-
- * The `stdin`, `stdout` and `stderr` attributes of the `mercurial.pycompat`
-   module were removed. Instead, the attributes of same name from the
-   `mercurial.utils.procutil` module should be used, which provide more
-   consistent behavior across Python versions and platforms.