mercurial/helptext/bundlespec.txt
author Manuel Jacob <me@manueljacob.de>
Mon, 11 Jul 2022 01:51:20 +0200
branchstable
changeset 49378 094a5fa3cf52
parent 43632 2e017696181f
child 49409 23dd636852b8
permissions -rw-r--r--
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.
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Mercurial supports generating standalone "bundle" files that hold repository
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data. These "bundles" are typically saved locally and used later or exchanged
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between different repositories, possibly on different machines. Example
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commands using bundles are :hg:`bundle` and :hg:`unbundle`.
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Generation of bundle files is controlled by a "bundle specification"
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("bundlespec") string. This string tells the bundle generation process how
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to create the bundle.
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A "bundlespec" string is composed of the following elements:
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type
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    A string denoting the bundle format to use.
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compression
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    Denotes the compression engine to use compressing the raw bundle data.
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parameters
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    Arbitrary key-value parameters to further control bundle generation.
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A "bundlespec" string has the following formats:
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<type>
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    The literal bundle format string is used.
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<compression>-<type>
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    The compression engine and format are delimited by a hyphen (``-``).
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Optional parameters follow the ``<type>``. Parameters are URI escaped
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``key=value`` pairs. Each pair is delimited by a semicolon (``;``). The
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first parameter begins after a ``;`` immediately following the ``<type>``
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value.
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Available Types
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===============
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The following bundle <type> strings are available:
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v1
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    Produces a legacy "changegroup" version 1 bundle.
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    This format is compatible with nearly all Mercurial clients because it is
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    the oldest. However, it has some limitations, which is why it is no longer
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    the default for new repositories.
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    ``v1`` bundles can be used with modern repositories using the "generaldelta"
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    storage format. However, it may take longer to produce the bundle and the
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    resulting bundle may be significantly larger than a ``v2`` bundle.
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    ``v1`` bundles can only use the ``gzip``, ``bzip2``, and ``none`` compression
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    formats.
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v2
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    Produces a version 2 bundle.
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    Version 2 bundles are an extensible format that can store additional
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    repository data (such as bookmarks and phases information) and they can
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    store data more efficiently, resulting in smaller bundles.
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    Version 2 bundles can also use modern compression engines, such as
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    ``zstd``, making them faster to compress and often smaller.
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Available Compression Engines
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=============================
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The following bundle <compression> engines can be used:
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.. bundlecompressionmarker
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Examples
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========
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``v2``
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    Produce a ``v2`` bundle using default options, including compression.
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``none-v1``
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    Produce a ``v1`` bundle with no compression.
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``zstd-v2``
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    Produce a ``v2`` bundle with zstandard compression using default
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    settings.
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``zstd-v1``
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    This errors because ``zstd`` is not supported for ``v1`` types.