view mercurial/help/templates.txt @ 26755:bb0b955d050d

streamclone: support for producing and consuming stream clone bundles

Up to this point, stream clones only existed as a dynamically generated
data format produced and consumed during streaming clones. In order to
support this efficient cloning format with the clone bundles feature, we
need a more formal, on disk representation of the streaming clone data.

This patch introduces a new "bundle" type for streaming clones. Unlike
existing bundles, it does not contain changegroup data. It does,
however, share the same concepts like the 4 byte header which identifies
the type of data that follows and the 2 byte abbreviation for
compression types (of which only "UN" is currently supported).

The new bundle format is essentially the existing stream clone version 1
data format with some headers at the beginning.

Content negotiation at stream clone request time checked for repository
format/requirements compatibility before initiating a stream clone. We
can't do active content negotiation when using clone bundles. So, we put
this set of requirements inside the payload so consumers have a built-in
mechanism for checking compatibility before reading and applying lots of
data. Of course, we will also advertise this requirements set in clone
bundles. But that's for another patch.

We currently don't have a mechanism to produce and consume this new
bundle format. This will be implemented in upcoming patches.

It's worth noting that if a legacy client attempts to `hg unbundle` a
stream clone bundle (with the "HGS1" header), it will abort with:
"unknown bundle version S1," which seems appropriate.

Mercurial allows you to customize output of commands through
templates. You can either pass in a template or select an existing
template-style from the command line, via the --template option.

You can customize output for any "log-like" command: log,
outgoing, incoming, tip, parents, and heads.

Some built-in styles are packaged with Mercurial. These can be listed
with :hg:`log --template list`. Example usage::

    $ hg log -r1.0::1.1 --template changelog

A template is a piece of text, with markup to invoke variable
expansion::

    $ hg log -r1 --template "{node}\n"
    b56ce7b07c52de7d5fd79fb89701ea538af65746

Strings in curly braces are called keywords. The availability of
keywords depends on the exact context of the templater. These
keywords are usually available for templating a log-like command:

.. keywordsmarker

The "date" keyword does not produce human-readable output. If you
want to use a date in your output, you can use a filter to process
it. Filters are functions which return a string based on the input
variable. Be sure to use the stringify filter first when you're
applying a string-input filter to a list-like input variable.
You can also use a chain of filters to get the desired output::

   $ hg tip --template "{date|isodate}\n"
   2008-08-21 18:22 +0000

List of filters:

.. filtersmarker

Note that a filter is nothing more than a function call, i.e.
``expr|filter`` is equivalent to ``filter(expr)``.

In addition to filters, there are some basic built-in functions:

.. functionsmarker

Also, for any expression that returns a list, there is a list operator:

- expr % "{template}"

As seen in the above example, "{template}" is interpreted as a template.
To prevent it from being interpreted, you can use an escape character "\{"
or a raw string prefix, "r'...'".

Some sample command line templates:

- Format lists, e.g. files::

   $ hg log -r 0 --template "files:\n{files % '  {file}\n'}"

- Join the list of files with a ", "::

   $ hg log -r 0 --template "files: {join(files, ', ')}\n"

- Modify each line of a commit description::

   $ hg log --template "{splitlines(desc) % '**** {line}\n'}"

- Format date::

   $ hg log -r 0 --template "{date(date, '%Y')}\n"

- Display date in UTC::

   $ hg log -r 0 --template "{localdate(date, 'UTC')|date}\n"

- Output the description set to a fill-width of 30::

   $ hg log -r 0 --template "{fill(desc, 30)}"

- Use a conditional to test for the default branch::

   $ hg log -r 0 --template "{ifeq(branch, 'default', 'on the main branch',
   'on branch {branch}')}\n"

- Append a newline if not empty::

   $ hg tip --template "{if(author, '{author}\n')}"

- Label the output for use with the color extension::

   $ hg log -r 0 --template "{label('changeset.{phase}', node|short)}\n"

- Invert the firstline filter, i.e. everything but the first line::

   $ hg log -r 0 --template "{sub(r'^.*\n?\n?', '', desc)}\n"

- Display the contents of the 'extra' field, one per line::

   $ hg log -r 0 --template "{join(extras, '\n')}\n"

- Mark the active bookmark with '*'::

   $ hg log --template "{bookmarks % '{bookmark}{ifeq(bookmark, active, '*')} '}\n"

- Find the previous release candidate tag, the distance and changes since the tag::

   $ hg log -r . --template "{latesttag('re:^.*-rc$') % '{tag}, {changes}, {distance}'}\n"

- Mark the working copy parent with '@'::

   $ hg log --template "{ifcontains(rev, revset('.'), '@')}\n"

- Show details of parent revisions::

   $ hg log --template "{revset('parents(%d)', rev) % '{desc|firstline}\n'}"

- Show only commit descriptions that start with "template"::

   $ hg log --template "{startswith('template', firstline(desc))}\n"

- Print the first word of each line of a commit message::

   $ hg log --template "{word(0, desc)}\n"