(*
Module: Dpkg
    Parses /etc/dpkg/dpkg.cfg

Author: Robin Lee Powell <rlpowell@digitalkingdom.org>

About: License
    This file, and the attendant test_dpgk.aug, are explicitly
    placed in the public domain.

About: Description
    dpkg.cfg is a simple list of options, the same ones as the
    command line options, with or without a value.

    The tree is a list of either comments or option/value pairs by
    name. Use "set" to set an option with a value, and "clear" for a
    bare option.

About: Usage Example

(start code)
    $ augtool -n
    augtool> ls /files/etc/dpkg/dpkg.cfg
    #comment[1] = dpkg configuration file
    #comment[2] = This file can contain default options for dpkg.  All command-line
    #comment[3] = options are allowed.  Values can be specified by putting them after
    #comment[4] = the option, separated by whitespace and/or an `=' sign.
    #comment[5] = Do not enable debsig-verify by default; since the distribution is not using
    #comment[6] = embedded signatures, debsig-verify would reject all packages.
    no-debsig = (none)
    #comment[7] = Log status changes and actions to a file.
    log = /var/log/dpkg.log
    augtool> get /files/etc/dpkg/dpkg.cfg/no-debsig
    /files/etc/dpkg/dpkg.cfg/no-debsig (none)
    augtool> get /files/etc/dpkg/dpkg.cfg/log
    /files/etc/dpkg/dpkg.cfg/log = /var/log/dpkg.log
    augtool> clear /files/etc/dpkg/dpkg.cfg/testopt
    augtool> set /files/etc/dpkg/dpkg.cfg/testopt2 test
    augtool> save
    Saved 1 file(s)
    augtool>
    $ cat /etc/dpkg/dpkg.cfg.augnew
    # dpkg configuration file
    #
    # This file can contain default options for dpkg.  All command-line
    # options are allowed.  Values can be specified by putting them after
    # the option, separated by whitespace and/or an `=' sign.
    #

    # Do not enable debsig-verify by default; since the distribution is not using
    # embedded signatures, debsig-verify would reject all packages.
    no-debsig

    # Log status changes and actions to a file.
    log /var/log/dpkg.log
    testopt
    testopt2 test
(end code)

*)

module Dpkg =
  autoload xfm

  let sep_tab = Util.del_ws_tab
  let sep_spc = Util.del_ws_spc
  let eol = del /[ \t]*\n/ "\n"

  let comment = Util.comment
  let empty   = Util.empty

  let word = /[^,# \n\t]+/
  let keyword = /[^,# \n\t\/]+/

  (* View: record
      Keyword, followed by optional whitespace and value, followed
      by EOL.

      The actual file specification doesn't require EOL, but the
      likelihood of the file not having one is pretty slim, and
      this way things we add have EOL.
  *)

  let record = [ key keyword . (sep_spc . store word)? . eol ]

  (* View: lns
      Any number of empty lines, comments, and records.
  *)
  let lns = ( empty | comment | record ) *

  let xfm = transform lns (incl "/etc/dpkg/dpkg.cfg")