view relnotes/5.8 @ 50092:010a1e73f69e stable

setup: further improve the error path for version retrieval

This is a new take at the problem that 8d390a13474d tried to tackle. There was
two issues after that previous improvement:

- the 0.0+ version could survive a bit too long and reaching the installer
  version and staying there.
- multiple use case where still failing.

So the new code is better at:
- always succeeding when running `make local` so that we can
  bootstrap a local version
- no using that fallback outside of `make local` to avoid distribution of
  version with the buggy version number.

The setup.py is a gigantic pile of spaghetti code, to the point where
pastafarian pilgrim started knocking at its core.

However I refrained from cleaning that up since the more to a `setup.cfg` means
this code should be deleted soon™.

== New Features ==
 
 * `hg purge` is now a core command using `--confirm` by default.
 
 * The `rev-branch-cache` is now updated incrementally whenever changesets
   are added.

 * The new options `experimental.bundlecompthreads` and
   `experimental.bundlecompthreads.<engine>` can be used to instruct
   the compression engines for bundle operations to use multiple threads
   for compression. The default is single threaded operation. Currently
   only supported for zstd.

== Default Format Change ==

These changes affects newly created repositories (or new clone) done with
Mercurial 5.8.

  * The `ZSTD` compression will now be used by default for new repositories
    when available. This compression format was introduced in Mercurial 5.0,
    released in May 2019. See `hg help config.format.revlog-compression` for
    details.

  * Mercurial installation built with the Rust parts will now use the
    "persistent nodemap" feature by default. This feature was introduced in
    Mercurial 5.4 (May 2020). However Mercurial instalation built without the
    fast Rust implementation will refuse to interract with them by default.
    This restriction can be lifted through configuration.

    See `hg help config.format.use-persistent-nodemap` for details

== New Experimental Features ==

 * There's a new `diff.merge` config option to show the changes
    relative to an automerge for merge changesets. This makes it
    easier to detect and review manual changes performed in merge
    changesets. It is supported by `hg diff --change`, `hg log -p`
    `hg incoming -p`, and `hg outgoing -p` so far.


== Bug Fixes ==

 * gracefully recover from inconsistent persistent-nodemap data from disk.


== Backwards Compatibility Changes ==

 * In normal repositories, the first parent of a changeset is not null,
   unless both parents are null (like the first changeset). Some legacy
   repositories violate this condition. The revlog code will now
   silentely swap the parents if this condition is tested. This can
   change the output of `hg log` when explicitly asking for first or
   second parent. The changesets "nodeid" are not affected.


== Internal API Changes ==

 * `changelog.branchinfo` is deprecated and will be removed after 5.8.
   It is superseded by `changelogrevision.branchinfo`.

 * Callbacks for revlog.addgroup and the changelog._nodeduplicatecallback hook
   now get a revision number as argument instead of a node.

 * revlog.addrevision returns the revision number instead of the node.

 * `nodes.nullid` and related constants are being phased out as part of
   the deprecation of SHA1. Repository instances and related classes
   provide access via `nodeconstants` and in some cases `nullid` attributes.