procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
== 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.