view mercurial/helptext/templates.txt @ 49030:75794847ef62

stringutil: try to avoid running `splitlines()` only to get first line

It's wasteful to call `splitlines()` and only get the first line from
it. However, Python doesn't seem to provide a built-in way of doing
just one split based on the set of bytes used by `splitlines()`. As a
workaround, we do an initial split on just LF and then call
`splitlines()` on the result. Thanks to Joerg for this suggestion. I
didn't bother to also split on CR, so users with old Mac editors (or
repos created by such editors) will not get this performance
improvement.

Differential Revision: https://phab.mercurial-scm.org/D12413

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

Keywords
========

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

Filters
=======

List of filters:

.. filtersmarker

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

Functions
=========

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

.. functionsmarker

Operators
=========

We provide a limited set of infix arithmetic operations on integers::

  + for addition
  - for subtraction
  * for multiplication
  / for floor division (division rounded to integer nearest -infinity)

Division fulfills the law x = x / y + mod(x, y).

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'...'``.

The dot operator can be used as a shorthand for accessing a sub item:

- ``expr.member`` is roughly equivalent to ``expr % '{member}'`` if ``expr``
  returns a non-list/dict. The returned value is not stringified.
- ``dict.key`` is identical to ``get(dict, 'key')``.

Aliases
=======

New keywords and functions can be defined in the ``templatealias`` section of
a Mercurial configuration file::

  <alias> = <definition>

Arguments of the form `a1`, `a2`, etc. are substituted from the alias into
the definition.

For example,

::

  [templatealias]
  r = rev
  rn = "{r}:{node|short}"
  leftpad(s, w) = pad(s, w, ' ', True)

defines two symbol aliases, ``r`` and ``rn``, and a function alias
``leftpad()``.

It's also possible to specify complete template strings, using the
``templates`` section. The syntax used is the general template string syntax.

For example,

::

  [templates]
  nodedate = "{node|short}: {date(date, "%Y-%m-%d")}\n"

defines a template, ``nodedate``, which can be called like::

  $ hg log -r . -Tnodedate

A template defined in ``templates`` section can also be referenced from
another template::

  $ hg log -r . -T "{rev} {nodedate}"

but be aware that the keywords cannot be overridden by templates. For example,
a template defined as ``templates.rev`` cannot be referenced as ``{rev}``.

A template defined in ``templates`` section may have sub templates which
are inserted before/after/between items::

  [templates]
  myjson = ' {dict(rev, node|short)|json}'
  myjson:docheader = '\{\n'
  myjson:docfooter = '\n}\n'
  myjson:separator = ',\n'

Examples
========

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"

- Join the list of files ending with ".py" with a ", "::

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

- Separate non-empty arguments by a " "::

   $ hg log -r 0 --template "{separate(' ', node, bookmarks, tags}\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"