view mercurial/help/bundlespec.txt @ 40324:6637b079ae45

lfs: autoload the extension when cloning from repo with lfs enabled

This is based on a patch by Gregory Szorc.  I made small adjustments to
clean up the messaging when the server has the extension enabled, but the
client has it disabled (to prevent autoloading).  Additionally, I added
a second server capability to distinguish between the server having the
extension enabled, and the server having LFS commits.  This helps prevent
unnecessary requirement propagation- the client shouldn't add a requirement
that the server doesn't have, just because the server had the extension
loaded.  The TODO I had about advertising a capability when the server can
natively serve up blobs isn't relevant anymore (we've had 2 releases that
support this), so I dropped it.

Currently, we lazily add the "lfs" requirement to a repo when we first
encounter LFS data. Due to a pretxnchangegroup hook that looks for LFS
data, this can happen at the end of clone.

Now that we have more control over how repositories are created, we can
do better.

This commit adds a repo creation option to add the "lfs" requirement.
hg.clone() sets this creation option if the remote peer is advertising
lfs usage (as opposed to just support needed to push).

So, what this change effectively does is have cloned repos
automatically inherit the "lfs" requirement.

Differential Revision: https://phab.mercurial-scm.org/D5130

Mercurial supports generating standalone "bundle" files that hold repository
data. These "bundles" are typically saved locally and used later or exchanged
between different repositories, possibly on different machines. Example
commands using bundles are :hg:`bundle` and :hg:`unbundle`.

Generation of bundle files is controlled by a "bundle specification"
("bundlespec") string. This string tells the bundle generation process how
to create the bundle.

A "bundlespec" string is composed of the following elements:

type
    A string denoting the bundle format to use.

compression
    Denotes the compression engine to use compressing the raw bundle data.

parameters
    Arbitrary key-value parameters to further control bundle generation.

A "bundlespec" string has the following formats:

<type>
    The literal bundle format string is used.

<compression>-<type>
    The compression engine and format are delimited by a hyphen (``-``).

Optional parameters follow the ``<type>``. Parameters are URI escaped
``key=value`` pairs. Each pair is delimited by a semicolon (``;``). The
first parameter begins after a ``;`` immediately following the ``<type>``
value.

Available Types
===============

The following bundle <type> strings are available:

v1
    Produces a legacy "changegroup" version 1 bundle.

    This format is compatible with nearly all Mercurial clients because it is
    the oldest. However, it has some limitations, which is why it is no longer
    the default for new repositories.

    ``v1`` bundles can be used with modern repositories using the "generaldelta"
    storage format. However, it may take longer to produce the bundle and the
    resulting bundle may be significantly larger than a ``v2`` bundle.

    ``v1`` bundles can only use the ``gzip``, ``bzip2``, and ``none`` compression
    formats.

v2
    Produces a version 2 bundle.

    Version 2 bundles are an extensible format that can store additional
    repository data (such as bookmarks and phases information) and they can
    store data more efficiently, resulting in smaller bundles.

    Version 2 bundles can also use modern compression engines, such as
    ``zstd``, making them faster to compress and often smaller.

Available Compression Engines
=============================

The following bundle <compression> engines can be used:

.. bundlecompressionmarker

Examples
========

``v2``
    Produce a ``v2`` bundle using default options, including compression.

``none-v1``
    Produce a ``v1`` bundle with no compression.

``zstd-v2``
    Produce a ``v2`` bundle with zstandard compression using default
    settings.

``zstd-v1``
    This errors because ``zstd`` is not supported for ``v1`` types.