view mercurial/help/environment.txt @ 25596:c1975809a6b5

templater: take any string literals as template, but not for rawstring (BC)

This patch series is intended to unify the interpretation of string literals.
It is breaking change that boldly assumes

 a. string literal "..." never contains template-like fragment or it is
    intended to be a template
 b. we tend to use raw string literal r"..." for regexp pattern in which "{"
    should have different meaning

Currently, we don't have a comprehensible rule how string literals are
evaluated in template functions. For example, fill() takes "initialindent"
and "hangindent" as templates, but not for "text", whereas "text" is a
template in pad() function.

  date(date, fmt)
  diff(includepattern, excludepattern)
  fill(text, width, initialident: T, hangindent: T)
  get(dict, key)
  if(expr, then: T, else: T)
  ifcontains(search, thing, then: T, else: T)
  ifeq(expr1, expr2, then: T, else: T)
  indent(text, indentchars, firstline)
  join(list, sep)
  label(label: T, expr: T)
  pad(text: T, width, fillchar, right)
  revset(query, formatargs...])
  rstdoc(text, style)
  shortest(node, minlength)
  startswith(pattern, text)
  strip(text, chars)
  sub(pattern, replacement, expression: T)
  word(number, text, separator)
  expr % template: T

  T: interpret "string" or r"rawstring" as template

This patch series adjusts the rule as follows:

 a. string literal, '' or "", starts template processing (BC)
 b. raw string literal, r'' or r"", disables both \-escape and template
    processing (BC, done by subsequent patches)
 c. fragment not surrounded by {} is non-templated string

  "ccc{'aaa'}{r'bbb'}"
   ------------------  *: template
   ---                 c: string
        ---            a: template
                ---    b: rawstring

Because this can eliminate the compilation of template arguments from the
evaluation phase, "hg log -Tdefault" gets faster.

  % cd mozilla-central
  % LANG=C HGRCPATH=/dev/null hg log -Tdefault -r0:10000 --time > /dev/null
  before: real 4.870 secs (user 4.860+0.000 sys 0.010+0.000)
  after:  real 3.480 secs (user 3.440+0.000 sys 0.030+0.000)

Also, this will allow us to parse nested templates at once for better error
indication.

HG
    Path to the 'hg' executable, automatically passed when running
    hooks, extensions or external tools. If unset or empty, this is
    the hg executable's name if it's frozen, or an executable named
    'hg' (with %PATHEXT% [defaulting to COM/EXE/BAT/CMD] extensions on
    Windows) is searched.

HGEDITOR
    This is the name of the editor to run when committing. See EDITOR.

    (deprecated, use configuration file)

HGENCODING
    This overrides the default locale setting detected by Mercurial.
    This setting is used to convert data including usernames,
    changeset descriptions, tag names, and branches. This setting can
    be overridden with the --encoding command-line option.

HGENCODINGMODE
    This sets Mercurial's behavior for handling unknown characters
    while transcoding user input. The default is "strict", which
    causes Mercurial to abort if it can't map a character. Other
    settings include "replace", which replaces unknown characters, and
    "ignore", which drops them. This setting can be overridden with
    the --encodingmode command-line option.

HGENCODINGAMBIGUOUS
    This sets Mercurial's behavior for handling characters with
    "ambiguous" widths like accented Latin characters with East Asian
    fonts. By default, Mercurial assumes ambiguous characters are
    narrow, set this variable to "wide" if such characters cause
    formatting problems.

HGMERGE
    An executable to use for resolving merge conflicts. The program
    will be executed with three arguments: local file, remote file,
    ancestor file.

    (deprecated, use configuration file)

HGRCPATH
    A list of files or directories to search for configuration
    files. Item separator is ":" on Unix, ";" on Windows. If HGRCPATH
    is not set, platform default search path is used. If empty, only
    the .hg/hgrc from the current repository is read.

    For each element in HGRCPATH:

    - if it's a directory, all files ending with .rc are added
    - otherwise, the file itself will be added

HGPLAIN
    When set, this disables any configuration settings that might
    change Mercurial's default output. This includes encoding,
    defaults, verbose mode, debug mode, quiet mode, tracebacks, and
    localization. This can be useful when scripting against Mercurial
    in the face of existing user configuration.

    Equivalent options set via command line flags or environment
    variables are not overridden.

HGPLAINEXCEPT
    This is a comma-separated list of features to preserve when
    HGPLAIN is enabled. Currently the only value supported is "i18n",
    which preserves internationalization in plain mode.

    Setting HGPLAINEXCEPT to anything (even an empty string) will
    enable plain mode.

HGUSER
    This is the string used as the author of a commit. If not set,
    available values will be considered in this order:

    - HGUSER (deprecated)
    - configuration files from the HGRCPATH
    - EMAIL
    - interactive prompt
    - LOGNAME (with ``@hostname`` appended)

    (deprecated, use configuration file)

EMAIL
    May be used as the author of a commit; see HGUSER.

LOGNAME
    May be used as the author of a commit; see HGUSER.

VISUAL
    This is the name of the editor to use when committing. See EDITOR.

EDITOR
    Sometimes Mercurial needs to open a text file in an editor for a
    user to modify, for example when writing commit messages. The
    editor it uses is determined by looking at the environment
    variables HGEDITOR, VISUAL and EDITOR, in that order. The first
    non-empty one is chosen. If all of them are empty, the editor
    defaults to 'vi'.

PYTHONPATH
    This is used by Python to find imported modules and may need to be
    set appropriately if this Mercurial is not installed system-wide.