Syntax for Mercurial Ignore Files

    Synopsis
    --------

    The Mercurial system uses a file called ".hgignore" in the root directory
    of a repository to control its behavior when it searches for files that it
    is not currently tracking.

    Description
    -----------

    The working directory of a Mercurial repository will often contain files
    that should not be tracked by Mercurial. These include backup files
    created by editors and build products created by compilers. These files
    can be ignored by listing them in a ".hgignore" file in the root of the
    working directory. The ".hgignore" file must be created manually. It is
    typically put under version control, so that the settings will propagate
    to other repositories with push and pull.

    An untracked file is ignored if its path relative to the repository root
    directory, or any prefix path of that path, is matched against any pattern
    in ".hgignore".

    For example, say we have an untracked file, "file.c", at "a/b/file.c"
    inside our repository. Mercurial will ignore "file.c" if any pattern in
    ".hgignore" matches "a/b/file.c", "a/b" or "a".

    In addition, a Mercurial configuration file can reference a set of per-
    user or global ignore files. See the "ignore" configuration key on the
    "[ui]" section of "hg help config" for details of how to configure these
    files.

    To control Mercurial's handling of files that it manages, many commands
    support the "-I" and "-X" options; see "hg help <command>" and "hg help
    patterns" for details.

    Syntax
    ------

    An ignore file is a plain text file consisting of a list of patterns, with
    one pattern per line. Empty lines are skipped. The "#" character is
    treated as a comment character, and the "\" character is treated as an
    escape character.

    Mercurial supports several pattern syntaxes. The default syntax used is
    Python/Perl-style regular expressions.

    To change the syntax used, use a line of the following form:

      syntax: NAME

    where "NAME" is one of the following:

    "regexp"
      Regular expression, Python/Perl syntax.

    "glob"
      Shell-style glob.

    The chosen syntax stays in effect when parsing all patterns that follow,
    until another syntax is selected.

    Neither glob nor regexp patterns are rooted. A glob-syntax pattern of the
    form "*.c" will match a file ending in ".c" in any directory, and a regexp
    pattern of the form "\.c$" will do the same. To root a regexp pattern,
    start it with "^".

    Note:
      Patterns specified in other than ".hgignore" are always rooted. Please
      see "hg help patterns" for details.

    Example
    -------

    Here is an example ignore file.

      # use glob syntax.
      syntax: glob

      *.elc
      *.pyc
      *~

      # switch to regexp syntax.
      syntax: regexp
      ^\.pc/