merge: add a config to allow conflict-free merge of changes on adjacent lines
This change adds a config to make it no longer a conflict to merge changes
made on adjacent lines.
The reason these changes are considered a conflict is that there's no
region of text at the relevant position (sync region) that's kept unchanged
by both sides of the merge.
The problem can be solved by making the sync regions being a bit more
powerful: we can keep a 0-length sync region if we find that
a block unchanged by one side is ajacent to a block unchanged by the
other side.
Since these 0-length sync regions are emitted using the ~same algorithm
as the normal non-empty sync regions, this change involves no arbitrary
decisions and I expect it to work pretty well.
0-length sync regions do create an ambiguity in a special case where two
pairs of adjacent regions "meet" at the same point. This corresponds to
an insertion made at the same place by the two sides of the merge, and
this still results in a conflict.
== 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 ==
* 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 ==
* 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 ==
* 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 ==
* 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.