#!/bin/sh
# $Id: patch-from-parent,v 1.2 2009/11/01 18:32:56 karl Exp $
# patch-from-parent
# Patch a file in CVS from a notional "parent" from which it "inherits".
# http://www.gnu.org/server/standards/boilerplate.html is one likely parent.

# Copyright (C) 2009 Free Software Foundation, Inc.
#
# 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 3 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 <http://www.gnu.org/licenses/>.
#
# Originally written by Reuben Thomas.

program=`basename $0`

if [ $# -lt 2 ]; then
    echo Usage: $program FILE PARENT-PATH
    echo Patch a file from a parent in a different repository
    echo FILE can be a relative path but PARENT-PATH must be absolute
    echo The previous version of the parent used is given by a Parent-Version: tag,
    echo which is updated by the script.
    echo
    echo Typical usage:
    echo
    echo   1. Run $program foo.html /path/to/parent.html
    echo   2. /path/to/parent.html will be CVS updated
    echo   3. foo.html will be updated
    echo   4. Resolve any conflicts
    echo
    echo A checkout of
    echo http://www.gnu.org/server/standards/boilerplate.html is one
    echo likely parent, and is the reason CVS is used.
    exit 1
fi

FILE=$1
FILE_PATH=`pwd`/$1
PARENT_FILE=$2
PARENT_BASE=`basename $PARENT_FILE`
PARENT_DIR=`dirname $PARENT_FILE`

CURRENT_VERSION=`sed -n '/Parent-Version:/{p;q;}' $FILE | sed -e 's/^.*Parent-Version: \([a-z0-9._-]\+\).*$/\1/i'`

( cd $PARENT_DIR
    NEW_VERSION=`cvs stat $PARENT_BASE | grep Working | cut -f 2`
    sed -i -e 's/\(Parent-Version: \)\([a-z0-9._-]\/+\)/\1'$NEW_VERSION'/i' $FILE_PATH
    cvs up $PARENT_BASE
    cvs diff -r $CURRENT_VERSION $PARENT_BASE ) |
patch $FILE