#!/usr/bin/perl -w
# git-debrebase
# Script helping make fast-forwarding histories while still rebasing
# upstream deltas when working on Debian packaging
#
# Copyright (C)2017 Ian Jackson
#
# 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/>.

use strict;
use Memoize;

use Debian::Dgit;

sub cfg ($) {
    my ($k) = @_;
    $/ = "\0";
    my @cmd = qw(git config -z);
    push @cmd, qw(--get-all) if wantarray;
    push @cmd, $k;
    my $out = cmdoutput @cmd;
    return split /\0/, $out;
}

memoize('cfg');

# usage
#  git debrebase launder

sub get_commit ($) {
    my ($objid) = @_;
    my ($type,$data) = git_cat_file $objid;
    die unless $type eq 'commit';
    $data =~ m/(?<=\n)\n/;
    return ($`,$');
}

memoize('get_commit');

sub DDEB () { return 0x1; }
sub DUPS () { return 0x2; }
sub DPAT () { return 0x4; }

sub launder () {
    # go through commits backwards
    # we generate two lists of commits to apply
    my (@deb_cl, @ups_cl);
    my $cur = git_rev_parse('HEAD');
    for (;;) {
	my ($h,$m) = get_commit $cur;
	my ($t) = $h =~ m/^tree (\w+)$/m;  defined $t or die $cur;
	my (@p) = $h =~ m/^parent (\w+)$/m;
	my (@d) = map { get_differs $t, $_ } @p;
	if (@p == 1) {
	    my ($d) = $d[0];
	    if ($d == DPAT) {
		# changes on debian/patches, discard it
		$cur = $p[0];
		next;
	    }
	    if ($d & DPAT) {
	    
}   

if ($ARGV[0] eq 'launder') {
    launder();
}

use Data::Dumper;
print Dumper(cfg('wombat.foo.bar'));