view mercurial/help/templates.txt @ 32924:f044295cdb7a

repair: move check for existing transaction earlier

Several benefits:

 * Gets close the comment describing it
 * Splits off unrelated comment about "backup" argument
 * Error checking is customarily done early
 * If we added an early return to the method, it would still
   consistently fail if there was an existing transaction (so
   we would find and fix that case quickly)

One test needs updating with for this change, because we no longer
create the backup bundle before we fail. I don't see much reason to
create that backup bundle. If some command was adding content and then
trying to strip it as well within the transaction, we would have a
backup for the user, but the risk of that not being discovered in
development seems very small.

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'...'``.

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}``.

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"