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✏️ Editing: dpkg-maintscript-helper

#!/bin/sh
#
# Copyright © 2007, 2011-2015 Guillem Jover <guillem@debian.org>
# Copyright © 2010 Raphaël Hertzog <hertzog@debian.org>
# Copyright © 2008 Joey Hess <joeyh@debian.org>
# Copyright © 2005 Scott James Remnant (original implementation on www.dpkg.org)
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

# The conffile related functions are inspired by
# https://wiki.debian.org/DpkgConffileHandling

# This script is documented in dpkg-maintscript-helper(1)

##
## Functions to remove an obsolete conffile during upgrade
##
rm_conffile() {
  local CONFFILE="$1"
  local LASTVERSION="$2"
  local PACKAGE="$3"

if [ "$LASTVERSION" = "--" ]; then
    LASTVERSION=""
    PACKAGE="$DPKG_MAINTSCRIPT_PACKAGE${DPKG_MAINTSCRIPT_ARCH:+:$DPKG_MAINTSCRIPT_ARCH}"
  fi
  if [ "$PACKAGE" = "--" -o -z "$PACKAGE" ]; then
    PACKAGE="$DPKG_MAINTSCRIPT_PACKAGE${DPKG_MAINTSCRIPT_ARCH:+:$DPKG_MAINTSCRIPT_ARCH}"
  fi
  # Skip remaining parameters up to --
  while [ "$1" != "--" -a $# -gt 0 ]; do
    shift
  done
  [ $# -gt 0 ] || badusage "missing arguments after --"
  shift

[ -n "$PACKAGE" ] || error "couldn't identify the package"
  [ -n "$1" ] || error "maintainer script parameters are missing"
  [ -n "$DPKG_MAINTSCRIPT_NAME" ] || \
    error "environment variable DPKG_MAINTSCRIPT_NAME is required"
  [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ] || \
    error "environment variable DPKG_MAINTSCRIPT_PACKAGE is required"
  [ "${CONFFILE}" != "${CONFFILE#/}" ] || \
    error "conffile '$CONFFILE' is not an absolute path"
  validate_optional_version "$LASTVERSION"

debug "Executing $0 rm_conffile in $DPKG_MAINTSCRIPT_NAME" \
        "of $DPKG_MAINTSCRIPT_PACKAGE"
  debug "CONFFILE=$CONFFILE PACKAGE=$PACKAGE" \
        "LASTVERSION=$LASTVERSION ACTION=$1 PARAM=$2"
  case "$DPKG_MAINTSCRIPT_NAME" in
  preinst)
    if [ "$1" = "install" -o "$1" = "upgrade" ] && [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      prepare_rm_conffile "$CONFFILE" "$PACKAGE"
    fi
    ;;
  postinst)
    if [ "$1" = "configure" ] && [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      finish_rm_conffile "$CONFFILE"
    fi
    ;;
  postrm)
    if [ "$1" = "purge" ]; then
      rm -f "$DPKG_ROOT$CONFFILE.dpkg-bak" \
            "$DPKG_ROOT$CONFFILE.dpkg-remove" \
            "$DPKG_ROOT$CONFFILE.dpkg-backup"
    fi
    if [ "$1" = "abort-install" -o "$1" = "abort-upgrade" ] &&
       [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      abort_rm_conffile "$CONFFILE" "$PACKAGE"
    fi
    ;;
  *)
    debug "$0 rm_conffile not required in $DPKG_MAINTSCRIPT_NAME"
    ;;
  esac
}

prepare_rm_conffile() {
  local CONFFILE="$1"
  local PACKAGE="$2"

[ -e "$DPKG_ROOT$CONFFILE" ] || return 0
  ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0

local md5sum old_md5sum
  md5sum="$(md5sum "$DPKG_ROOT$CONFFILE" | sed -e 's/ .*//')"
  old_md5sum="$(dpkg-query -W -f='${Conffiles}' "$PACKAGE" | \
    sed -n -e "\\'^ $CONFFILE ' { s/ obsolete$//; s/.* //; p }")"
  if [ "$md5sum" != "$old_md5sum" ]; then
    mv -f "$DPKG_ROOT$CONFFILE" "$DPKG_ROOT$CONFFILE.dpkg-backup"
  else
    mv -f "$DPKG_ROOT$CONFFILE" "$DPKG_ROOT$CONFFILE.dpkg-remove"
  fi
}

finish_rm_conffile() {
  local CONFFILE="$1"

if [ -e "$DPKG_ROOT$CONFFILE.dpkg-backup" ]; then
    echo "Obsolete conffile $DPKG_ROOT$CONFFILE has been modified by you."
    echo "Saving as $DPKG_ROOT$CONFFILE.dpkg-bak ..."
    mv -f "$DPKG_ROOT$CONFFILE.dpkg-backup" "$DPKG_ROOT$CONFFILE.dpkg-bak"
  fi
  if [ -e "$DPKG_ROOT$CONFFILE.dpkg-remove" ]; then
    echo "Removing obsolete conffile $DPKG_ROOT$CONFFILE ..."
    rm -f "$DPKG_ROOT$CONFFILE.dpkg-remove"
  fi
}

abort_rm_conffile() {
  local CONFFILE="$1"
  local PACKAGE="$2"

ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0

if [ -e "$DPKG_ROOT$CONFFILE.dpkg-remove" ]; then
    echo "Reinstalling $DPKG_ROOT$CONFFILE that was moved away"
    mv "$DPKG_ROOT$CONFFILE.dpkg-remove" "$DPKG_ROOT$CONFFILE"
  fi
  if [ -e "$DPKG_ROOT$CONFFILE.dpkg-backup" ]; then
    echo "Reinstalling $DPKG_ROOT$CONFFILE that was backed-up"
    mv "$DPKG_ROOT$CONFFILE.dpkg-backup" "$DPKG_ROOT$CONFFILE"
  fi
}

##
## Functions to rename a conffile during upgrade
##
mv_conffile() {
  local OLDCONFFILE="$1"
  local NEWCONFFILE="$2"
  local LASTVERSION="$3"
  local PACKAGE="$4"

[ -n "$PACKAGE" ] || error "couldn't identify the package"
  [ -n "$1" ] || error "maintainer script parameters are missing"
  [ -n "$DPKG_MAINTSCRIPT_NAME" ] || \
    error "environment variable DPKG_MAINTSCRIPT_NAME is required"
  [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ] || \
    error "environment variable DPKG_MAINTSCRIPT_PACKAGE is required"
  [ "${OLDCONFFILE}" != "${OLDCONFFILE#/}" ] || \
    error "old-conffile '$OLDCONFFILE' is not an absolute path"
  [ "${NEWCONFFILE}" != "${NEWCONFFILE#/}" ] || \
    error "new-conffile '$NEWCONFFILE' is not an absolute path"
  validate_optional_version "$LASTVERSION"

debug "Executing $0 mv_conffile in $DPKG_MAINTSCRIPT_NAME" \
        "of $DPKG_MAINTSCRIPT_PACKAGE"
  debug "CONFFILE=$OLDCONFFILE -> $NEWCONFFILE PACKAGE=$PACKAGE" \
        "LASTVERSION=$LASTVERSION ACTION=$1 PARAM=$2"
  case "$DPKG_MAINTSCRIPT_NAME" in
  preinst)
    if [ "$1" = "install" -o "$1" = "upgrade" ] && [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      prepare_mv_conffile "$OLDCONFFILE" "$PACKAGE"
    fi
    ;;
  postinst)
    if [ "$1" = "configure" ] && [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      finish_mv_conffile "$OLDCONFFILE" "$NEWCONFFILE" "$PACKAGE"
    fi
    ;;
  postrm)
    if [ "$1" = "abort-install" -o "$1" = "abort-upgrade" ] &&
       [ -n "$2" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      abort_mv_conffile "$OLDCONFFILE" "$PACKAGE"
    fi
    ;;
  *)
    debug "$0 mv_conffile not required in $DPKG_MAINTSCRIPT_NAME"
    ;;
  esac
}

prepare_mv_conffile() {
  local CONFFILE="$1"
  local PACKAGE="$2"

[ -e "$DPKG_ROOT$CONFFILE" ] || return 0

ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0

local md5sum old_md5sum
  md5sum="$(md5sum "$DPKG_ROOT$CONFFILE" | sed -e 's/ .*//')"
  old_md5sum="$(dpkg-query -W -f='${Conffiles}' "$PACKAGE" | \
    sed -n -e "\\'^ $CONFFILE ' { s/ obsolete$//; s/.* //; p }")"
  if [ "$md5sum" = "$old_md5sum" ]; then
    mv -f "$DPKG_ROOT$CONFFILE" "$DPKG_ROOT$CONFFILE.dpkg-remove"
  fi
}

finish_mv_conffile() {
  local OLDCONFFILE="$1"
  local NEWCONFFILE="$2"
  local PACKAGE="$3"

rm -f "$DPKG_ROOT$OLDCONFFILE.dpkg-remove"

[ -e "$DPKG_ROOT$OLDCONFFILE" ] || return 0
  ensure_package_owns_file "$PACKAGE" "$OLDCONFFILE" || return 0

echo "Preserving user changes to $DPKG_ROOT$NEWCONFFILE (renamed from $DPKG_ROOT$OLDCONFFILE)..."
  if [ -e "$DPKG_ROOT$NEWCONFFILE" ]; then
    mv -f "$DPKG_ROOT$NEWCONFFILE" "$DPKG_ROOT$NEWCONFFILE.dpkg-new"
  fi
  mv -f "$DPKG_ROOT$OLDCONFFILE" "$DPKG_ROOT$NEWCONFFILE"
}

abort_mv_conffile() {
  local CONFFILE="$1"
  local PACKAGE="$2"

ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0

if [ -e "$DPKG_ROOT$CONFFILE.dpkg-remove" ]; then
    echo "Reinstalling $DPKG_ROOT$CONFFILE that was moved away"
    mv "$DPKG_ROOT$CONFFILE.dpkg-remove" "$DPKG_ROOT$CONFFILE"
  fi
}

##
## Functions to replace a symlink with a directory
##
symlink_to_dir() {
  local SYMLINK="$1"
  local SYMLINK_TARGET="$2"
  local LASTVERSION="$3"
  local PACKAGE="$4"

# Skip remaining parameters up to --
  while [ "$1" != "--" -a $# -gt 0 ]; do
    shift
  done
  [ $# -gt 0 ] || badusage "missing arguments after --"
  shift

[ -n "$DPKG_MAINTSCRIPT_NAME" ] || \
    error "environment variable DPKG_MAINTSCRIPT_NAME is required"
  [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ] || \
    error "environment variable DPKG_MAINTSCRIPT_PACKAGE is required"
  [ -n "$PACKAGE" ] || error "cannot identify the package"
  [ -n "$SYMLINK" ] || error "symlink parameter is missing"
  [ "${SYMLINK#/}" = "$SYMLINK" ] && \
    error "symlink pathname is not an absolute path"
  [ "${SYMLINK%/}" = "$SYMLINK" ] || \
    error "symlink pathname ends with a slash"
  [ -n "$SYMLINK_TARGET" ] || error "original symlink target is missing"
  [ -n "$1" ] || error "maintainer script parameters are missing"
  validate_optional_version "$LASTVERSION"

debug "Executing $0 symlink_to_dir in $DPKG_MAINTSCRIPT_NAME" \
        "of $DPKG_MAINTSCRIPT_PACKAGE"
  debug "SYMLINK=$SYMLINK -> $SYMLINK_TARGET PACKAGE=$PACKAGE" \
        "LASTVERSION=$LASTVERSION ACTION=$1 PARAM=$2"

case "$DPKG_MAINTSCRIPT_NAME" in
  preinst)
    if [ "$1" = "install" -o "$1" = "upgrade" ] &&
       [ -n "$2" ] && [ -h "$DPKG_ROOT$SYMLINK" ] &&
       symlink_match "$SYMLINK" "$SYMLINK_TARGET" &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      mv -f "$DPKG_ROOT$SYMLINK" "$DPKG_ROOT${SYMLINK}.dpkg-backup"
    fi
    ;;
  postinst)
    # We cannot bail depending on the version, as here we only
    # know what was the last configured version, and we might
    # have been unpacked, then upgraded with an unpack and thus
    # never been configured before.
    if [ "$1" = "configure" ] &&
       [ -h "$DPKG_ROOT${SYMLINK}.dpkg-backup" ] &&
       symlink_match "${SYMLINK}.dpkg-backup" "$SYMLINK_TARGET"
    then
      rm -f "$DPKG_ROOT${SYMLINK}.dpkg-backup"
    fi
    ;;
  postrm)
    if [ "$1" = "purge" ] && [ -h "$DPKG_ROOT${SYMLINK}.dpkg-backup" ]; then
      rm -f "$DPKG_ROOT${SYMLINK}.dpkg-backup"
    fi
    if [ "$1" = "abort-install" -o "$1" = "abort-upgrade" ] &&
       [ -n "$2" ] &&
       [ ! -e "$DPKG_ROOT$SYMLINK" ] &&
       [ -h "$DPKG_ROOT${SYMLINK}.dpkg-backup" ] &&
       symlink_match "${SYMLINK}.dpkg-backup" "$SYMLINK_TARGET" &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      echo "Restoring backup of $DPKG_ROOT$SYMLINK ..."
      mv "$DPKG_ROOT${SYMLINK}.dpkg-backup" "$DPKG_ROOT$SYMLINK"
    fi
    ;;
  *)
    debug "$0 symlink_to_dir not required in $DPKG_MAINTSCRIPT_NAME"
    ;;
  esac
}

##
## Functions to replace a directory with a symlink
##
dir_to_symlink() {
  local PATHNAME="${1%/}"
  local SYMLINK_TARGET="$2"
  local LASTVERSION="$3"
  local PACKAGE="$4"

# Skip remaining parameters up to --
  while [ "$1" != "--" -a $# -gt 0 ]; do
    shift
  done
  [ $# -gt 0 ] || badusage "missing arguments after --"
  shift

[ -n "$DPKG_MAINTSCRIPT_NAME" ] || \
    error "environment variable DPKG_MAINTSCRIPT_NAME is required"
  [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ] || \
    error "environment variable DPKG_MAINTSCRIPT_PACKAGE is required"
  [ -n "$PACKAGE" ] || error "cannot identify the package"
  [ -n "$PATHNAME" ] || error "directory parameter is missing"
  [ "${PATHNAME#/}" = "$PATHNAME" ] && \
    error "directory parameter is not an absolute path"
  [ -n "$SYMLINK_TARGET" ] || error "new symlink target is missing"
  [ -n "$1" ] || error "maintainer script parameters are missing"
  validate_optional_version "$LASTVERSION"

debug "Executing $0 dir_to_symlink in $DPKG_MAINTSCRIPT_NAME" \
        "of $DPKG_MAINTSCRIPT_PACKAGE"
  debug "PATHNAME=$PATHNAME SYMLINK_TARGET=$SYMLINK_TARGET" \
        "PACKAGE=$PACKAGE LASTVERSION=$LASTVERSION ACTION=$1 PARAM=$2"

case "$DPKG_MAINTSCRIPT_NAME" in
  preinst)
    if [ "$1" = "install" -o "$1" = "upgrade" ] &&
       [ -n "$2" ] &&
       [ ! -h "$DPKG_ROOT$PATHNAME" ] &&
       [ -d "$DPKG_ROOT$PATHNAME" ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      prepare_dir_to_symlink "$PACKAGE" "$PATHNAME"
    fi
    ;;
  postinst)
    # We cannot bail depending on the version, as here we only
    # know what was the last configured version, and we might
    # have been unpacked, then upgraded with an unpack and thus
    # never been configured before.
    if [ "$1" = "configure" ] &&
       [ -d "$DPKG_ROOT${PATHNAME}.dpkg-backup" ] &&
       [ ! -h "$DPKG_ROOT$PATHNAME" ] &&
       [ -d "$DPKG_ROOT$PATHNAME" ] &&
       [ -f "$DPKG_ROOT$PATHNAME/.dpkg-staging-dir" ]; then
      finish_dir_to_symlink "$PATHNAME" "$SYMLINK_TARGET"
    fi
    ;;
  postrm)
    if [ "$1" = "purge" ] &&
       [ -d "$DPKG_ROOT${PATHNAME}.dpkg-backup" ]; then
      rm -rf "$DPKG_ROOT${PATHNAME}.dpkg-backup"
    fi
    if [ "$1" = "abort-install" -o "$1" = "abort-upgrade" ] &&
       [ -n "$2" ] &&
       [ -d "$DPKG_ROOT${PATHNAME}.dpkg-backup" ] &&
       [ $ ! -h "$DPKG_ROOT$PATHNAME" -a \
            -d "$DPKG_ROOT$PATHNAME" -a \
            -f "$DPKG_ROOT$PATHNAME/.dpkg-staging-dir" $ -o \
         $ -h "$DPKG_ROOT$PATHNAME" -a \
            \( "$(readlink "$DPKG_ROOT$PATHNAME")" = "$SYMLINK_TARGET" -o \
               "$(dpkg-realpath "$PATHNAME")" = "$SYMLINK_TARGET" $ \) ] &&
       dpkg --compare-versions -- "$2" le-nl "$LASTVERSION"; then
      abort_dir_to_symlink "$PATHNAME"
    fi
    ;;
  *)
    debug "$0 dir_to_symlink not required in $DPKG_MAINTSCRIPT_NAME"
    ;;
  esac
}

prepare_dir_to_symlink()
{
  local PACKAGE="$1"
  local PATHNAME="$2"

local LINE
  # If there are conffiles we should not perform the switch.
  dpkg-query -W -f='${Conffiles}\n' "$PACKAGE" | while read -r LINE; do
    case "$LINE" in
    "$PATHNAME"/*)
      error "directory '$PATHNAME' contains conffiles," \
            "cannot switch to symlink"
      ;;
    esac
  done

# If there are locally created files or files owned by another package
  # we should not perform the switch.
  export DPKG_MAINTSCRIPT_HELPER_INTERNAL_API="$version"
  find "$DPKG_ROOT$PATHNAME" -print0 | \
    xargs -0 -n1 "$0" _internal_pkg_must_own_file "$PACKAGE" || \
    error "directory '$PATHNAME' contains files not owned by" \
          "package $PACKAGE, cannot switch to symlink"
  unset DPKG_MAINTSCRIPT_HELPER_INTERNAL_API

# At this point, we know that the directory either contains no files,
  # or only non-conffiles owned by the package.
  #
  # To do the switch we cannot simply replace it with the final symlink
  # just yet, because dpkg needs to remove any file present in the old
  # package that have disappeared in the new one, and we do not want to
  # lose files resolving to the same pathname in the symlink target.
  #
  # We cannot replace the directory with a staging symlink either,
  # because dpkg will update symlinks to their new target.
  #
  # So we need to create a staging directory, to avoid removing files
  # from other packages, and to trap any new files in the directory
  # to move them to their correct place later on.
  mv -f "$DPKG_ROOT$PATHNAME" "$DPKG_ROOT${PATHNAME}.dpkg-backup"
  mkdir "$DPKG_ROOT$PATHNAME"

# Mark it as a staging directory, so that we can track things.
  touch "$DPKG_ROOT$PATHNAME/.dpkg-staging-dir"
}

finish_dir_to_symlink()
{
  local PATHNAME="$1"
  local SYMLINK_TARGET="$2"

# Move the contents of the staging directory to the symlink target,
  # as those are all new files installed between this package being
  # unpacked and configured.
  local ABS_SYMLINK_TARGET
  if [ "${SYMLINK_TARGET#/}" = "$SYMLINK_TARGET" ]; then
    ABS_SYMLINK_TARGET="$(dirname "$PATHNAME")/$SYMLINK_TARGET"
  else
    ABS_SYMLINK_TARGET="$SYMLINK_TARGET"
  fi
  rm "$DPKG_ROOT$PATHNAME/.dpkg-staging-dir"
  find "$DPKG_ROOT$PATHNAME" -mindepth 1 -maxdepth 1 -print0 | \
    xargs -0 -i% mv -f "%" "$DPKG_ROOT$ABS_SYMLINK_TARGET/"

# Remove the staging directory.
  rmdir "$DPKG_ROOT$PATHNAME"

# Do the actual switch.
  ln -s "$SYMLINK_TARGET" "$DPKG_ROOT$PATHNAME"

# We are left behind the old files owned by this package in the backup
  # directory, just remove it.
  rm -rf "$DPKG_ROOT${PATHNAME}.dpkg-backup"
}

abort_dir_to_symlink()
{
  local PATHNAME="$1"

echo "Restoring backup of $DPKG_ROOT$PATHNAME ..."
  if [ -h "$DPKG_ROOT$PATHNAME" ]; then
    rm -f "$DPKG_ROOT$PATHNAME"
  else
    # The staging directory must be empty, as no other package
    # should have been unpacked in between.
    rm -f "$DPKG_ROOT$PATHNAME/.dpkg-staging-dir"
    rmdir "$DPKG_ROOT$PATHNAME"
  fi

mv "$DPKG_ROOT${PATHNAME}.dpkg-backup" "$DPKG_ROOT$PATHNAME"
}

# Common functions
validate_optional_version() {
  local VERSION="$1"

if [ -z "$VERSION" ]; then
    return
  fi

if ! VERSIONCHECK=$(dpkg --validate-version -- "$VERSION" 2>&1); then
    error "$VERSIONCHECK"
  fi
}

ensure_package_owns_file() {
  local PACKAGE="$1"
  local FILE="$2"

if ! dpkg-query -L "$PACKAGE" | grep -F -q -x "$FILE"; then
    debug "File '$FILE' not owned by package " \
          "'$PACKAGE', skipping $command"
    return 1
  fi
  return 0
}

internal_pkg_must_own_file()
{
  local PACKAGE="$1"
  local FILE="${2##$DPKG_ROOT}"

if [ "$DPKG_MAINTSCRIPT_HELPER_INTERNAL_API" != "$version" ]; then
    error "internal API used by external command"
  fi

if ! ensure_package_owns_file "$PACKAGE" "$FILE"; then
    error "file '$FILE' not owned by package '$PACKAGE'"
  fi
  return 0
}

symlink_match()
{
  local SYMLINK="$1"
  local SYMLINK_TARGET="$2"

[ "$(readlink "$DPKG_ROOT$SYMLINK")" = "$SYMLINK_TARGET" ] || \
  [ "$(dpkg-realpath "$SYMLINK")" = "$SYMLINK_TARGET" ]
}

usage() {
  cat <<END
Usage: $PROGNAME <command> <parameter>... -- <maintainer-script-parameter>...

Commands:
  supports <command>
        Returns 0 (success) if the given command is supported, 1 otherwise.
  rm_conffile <conffile> [<last-version> [<package>]]
        Remove obsolete conffile. Must be called in preinst, postinst and
        postrm.
  mv_conffile <old-conf> <new-conf> [<last-version> [<package>]]
        Rename a conffile. Must be called in preinst, postinst and postrm.
  symlink_to_dir <pathname> <old-symlink-target> [<last-version> [<package>]]
        Replace a symlink with a directory. Must be called in preinst,
        postinst and postrm.
  dir_to_symlink <pathname> <new-symlink-target> [<last-version> [<package>]]
        Replace a directory with a symlink. Must be called in preinst,
        postinst and postrm.
  help
  -?, --help
        Show this help message.
      --version
        Show the version.
END
}

# Main code
set -e

PROGNAME=$(basename "$0")
version="1.20.9"
DPKG_ROOT=${DPKG_ROOT:+$(realpath "$DPKG_ROOT")}
# Remove default root dir.
if [ "$DPKG_ROOT" = "/" ]; then
  DPKG_ROOT=""
fi
export DPKG_ROOT

PKGDATADIR_DEFAULT='/usr/share/dpkg'
PKGDATADIR="${DPKG_DATADIR:-$PKGDATADIR_DEFAULT}"

. "$PKGDATADIR/sh/dpkg-error.sh"

setup_colors

command="$1"
[ $# -gt 0 ] || badusage "missing command"
shift

case "$command" in
supports)
  case "$1" in
  rm_conffile|mv_conffile|symlink_to_dir|dir_to_symlink)
    code=0
    ;;
  *)
    code=1
    ;;
  esac
  if [ -z "$DPKG_MAINTSCRIPT_NAME" ]; then
    warning "environment variable DPKG_MAINTSCRIPT_NAME missing"
    code=1
  fi
  if [ -z "$DPKG_MAINTSCRIPT_PACKAGE" ]; then
    warning "environment variable DPKG_MAINTSCRIPT_PACKAGE missing"
    code=1
  fi
  exit $code
  ;;
rm_conffile)
  rm_conffile "$@"
  ;;
mv_conffile)
  mv_conffile "$@"
  ;;
symlink_to_dir)
  symlink_to_dir "$@"
  ;;
dir_to_symlink)
  dir_to_symlink "$@"
  ;;
_internal_pkg_must_own_file)
  # This is an internal command, must not be used outside this program.
  internal_pkg_must_own_file "$@"
  ;;
--help|help|-?)
  usage
  ;;
--version)
  cat <<END
Debian $PROGNAME version $version.

This is free software; see the GNU General Public License version 2 or
later for copying conditions. There is NO warranty.
END
  ;;
*)
  badusage "command $command is unknown
Hint: upgrading dpkg to a newer version might help."
esac

exit 0

MR SKB