#!/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 .
# usages:
# git-debrebase status
# git-debrebase start # like ffqrebase start + debrebase launder
# git-debrebase new-upstream [stuff] # see below
# git-debrebase # does debrebase start if necessary
#
# git-debrebase analyse
# git-debrebase launder # prints breakwater tip
# git-debrebase create-new-upstream-breakwater [-f] ...
#
# is
# [,][:][+][,...]
#
# if initial comma is supplied, entries are not positional. Unspecified
# means root (and there may be only one).
# xxx want auto branch names
# xxx too complicated
# how about for now
# [+] [ [+]...]
# ? plus options
# --new-upstream-different-subtrees
#
# automatic case
# git-debrebase new-upstream
# - previous breakwater merge must be gdr-generated
# - orig set is the same as before
# - implicitly uses upstream branches according to orig set
# - not all upstream branches need be updated
# - insists on fast-forward of each branch, unless
# --force (or --force=[/])
# branch set adjustments
# git-debrebase new-upstream --add /
# git-debrebase new-upstream --rm /
# git-debrebase new-upstream / [/ ...]
# - orig set is adjusted
# - otherwise like auto (--add is not checked for ffness, obv)
# - multiple --add and --rm may be specified
# - --add makes new upstream the last contributor
# explicit
# git-debrebase / [] [/ [] ...]
# - orig set is precisely as specified now
# - previous breakwater merge is irrelevant
# - no fast forward checks
# for now only explicit with commitids
# implicitly uses `upstream'
# # (or multiple other branches)
# git-debrebase new-upstream \
# [/]=
# UPSTREAM[,[[SUBDIR:]SUBUPSTREAM]
# default for SUBDIR: is from previous upstream merge[xxx terminology]
#
#
#xxx
# when starting must record original start (for ff)
# and new rebase basis
#
# git-ffqrebase start [BASE]
# # records previous HEAD so it can be overwritten
# # records base for future git-ffqrebase
# git-ffqrebase set-base BASE
# git-ffqrebase
# git-ffqrebase finish
# git-ffqrebase status [BRANCH]
#
# refs/ffqrebase-prev/BRANCH BRANCH may be refs/...; if not it means
# refs/ffqrebase-base/BRANCH refs/heads/BRANCH
# zero, one, or both of these may exist
#
# git-debrebase without start, if already started, is willing
# to strip pseudomerges provided that they overwrite exactly
# the previous HEAD
# xxxx is this right ? what matters is have we pushed
# I think in fact the right answer is:
# git-debrebase always strips out pseudomerges from its branch
# a pseudomerge is put in at the time we want to push
# at that time, we make a pseudomerge of the remote tracking
# branch (if raw git) or the dgit view (if dgit)
# for raw git git-ffqrebase, do want preciseley to record
# value of remote tracking branch or our branch, on start, so we
# overwrite only things we intend to
# the previous pseudomerge check for tags and remote branches ?
use strict;
use Memoize;
use Carp;
use Data::Dumper;
use Debian::Dgit qw(:DEFAULT $wa);
sub badusage ($) {
my ($m) = @_;
die "bad usage: $m\n";
}
sub cfg ($) {
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/, $out;
}
memoize('cfg');
sub get_commit ($) {
my ($objid) = @_;
my ($type,$data) = git_cat_file $objid;
die unless $type eq 'commit';
$data =~ m/(?<=\n)\n/;
return ($`,$');
}
sub D_DEB () { return 0x1; } # debian/ (not including debian/patches/)
sub D_UPS () { return 0x2; } # upstream files
sub D_PAT_ADD () { return 0x4; } # debian/patches/ extra patches at end
sub D_PAT_OTH () { return 0x8; } # debian/patches other changes
our $rd = ".git/git-debrebase";
our $ud = "$rd/work";
our @git = qw(git);
sub commit_pr_info ($) {
my ($r) = @_;
return Data::Dumper->dump([$r], [qw(commit)]);
}
sub calculate_committer_authline () {
my $c = cmdoutput @git, qw(commit-tree --no-gpg-sign -m),
'DUMMY COMMIT (git-debrebase)', "HEAD:";
my ($h,$m) = get_commit $c;
$h =~ m/^committer .*$/m or confess "($h) ?";
return $&;
}
# classify returns an info hash like this
# CommitId => $objid
# Hdr => # commit headers, including 1 final newline
# Msg => # commit message (so one newline is dropped)
# Tree => $treeobjid
# Type => (see below)
# Parents = [ {
# Ix => $index # ie 0, 1, 2, ...
# CommitId
# Differs => return value from get_differs
# IsOrigin
# IsDggitImport => 'orig' 'tarball' 'unpatched' 'package' (as from dgit)
# } ...]
# NewMsg => # commit message, but with any [dgit import ...] edited
# # to say "[was: ...]"
#
# Types:
# Packaging
# Upstream
# AddPatches
# Mixed
# Unknown
#
# Pseudomerge
# has additional entres in classification result
# Overwritten = [ subset of Parents ]
# Contributor = $the_remaining_Parent
#
# DgitImportUnpatched
# has additional entry in classification result
# OrigParents = [ subset of Parents ]
#
# BreakwaterUpstreamMerge
# has additional entry in classification result
# OrigParents = [ subset of Parents ]
sub classify ($) {
my ($objid) = @_;
my ($h,$m) = get_commit $objid;
my ($t) = $h =~ m/^tree (\w+)$/m or die $objid;
my (@ph) = $h =~ m/^parent (\w+)$/m;
my @p;
my $r = {
CommitId => $objid,
Hdr => $h,
Msg => $m,
Tree => $t,
Parents => \@p,
};
foreach my $ph (@ph) {
push @p, {
Ix => $#p,
CommitId => $ph,
Differs => (get_differs $t, $ph),
};
}
my $classify = sub {
my ($type, @rest) = @_;
$r = { %$r, Type => $type, @rest };
return $r;
};
my $unknown = sub {
my ($why) = @_;
$r = { %$r, Type => qw(Unknown) };
return $r;
};
if (@p == 1) {
my $d = $r->{Parents}[0]{Differs};
if ($d == D_PAT_ADD) {
return $classify->(qw(AddPatches));
} elsif ($d & (D_PAT_ADD|D_PAT_OTH)) {
return $unknown->("edits debian/patches");
} elsif ($d == D_DEB) {
my ($ty,$dummy) = git_cat_file "$ph[0]:debian";
if ($ty eq 'tree') {
return $classify->(qw(Packaging));
} elsif ($ty eq 'missing') {
return $classify->(qw(BreakwaterStart));
} else {
return $unknown->("parent's debian is not a directory");
}
} elsif ($d == D_UPS) {
return $classify->(qw(Upstream));
} elsif ($d == (D_DEB|D_UPS)) {
return $classify->(qw(Mixed));
} elsif ($d == 0) {
return $unknown->("no changes");
} else {
confess "internal error $objid ?";
}
}
if (!@p) {
return $unknown->("origin commit");
}
my @identical = grep { !$_->{Differs} } @p;
if (@p == 2 && @identical == 1) {
my @overwritten = grep { $_->{Differs} } @p;
confess "internal error $objid ?" unless @overwritten==1;
return $classify->(qw(Pseudomerge),
Overwritten => $overwritten[0],
Contributor => $identical[0]);
}
if (@p == 2 && @identical == 2) {
my @bytime = nsort_by {
my ($ph,$pm) = get_commit $_->{CommitId};
$ph =~ m/^committer .* (\d+) [-+]\d+$/m or die "$_->{CommitId} ?";
$1;
} @p;
return $classify->(qw(Pseudomerge),
SubType => qw(Ambiguous),
Overwritten => $bytime[0],
Contributor => $bytime[1]);
}
foreach my $p (@p) {
my ($p_h, $p_m) = get_commit $p;
$p->{IsOrigin} = $p_h !~ m/^parent \w+$/m;
($p->{IsDgitImport},) = $p_m =~ m/^\[dgit import ([0-9a-z]+) .*\]$/m;
}
my @orig_ps = grep { ($_->{IsDgitImport}//'X') eq 'orig' } @p;
my $m2 = $m;
if (!(grep { !$_->{IsOrigin} } @p) and
(@orig_ps >= @p - 1) and
$m2 =~ s{^\[(dgit import unpatched .*)\]$}{[was: $1]}m) {
$r->{NewMsg} = $m2;
return $classify->(qw(DgitImportUnpatched),
OrigParents => \@orig_ps);
}
my ($stype, $series) = git_cat_file "$t:debian/patches/series";
my $haspatches = $stype ne 'missing' && $series =~ m/^\s*[^#\n\t ]/m;
# How to decide about l/r ordering of breakwater merges ? git
# --topo-order prefers to expand 2nd parent first. There's
# already an easy rune to look for debian/ history anyway (git log
# debian/) so debian breakwater branch should be 1st parent; that
# way also there's also an easy rune to look for the upstream
# patches (--topo-order).
if (@p == 2 &&
!$haspatches &&
!$p[0]{IsOrigin} && # breakwater merge never starts with an origin
!($p[0]{Differs} & ~D_DEB) &&
!($p[1]{Differs} & ~D_UPS)) {
return $classify->(qw(BreakwaterUpstreamMerge),
OrigParents => [ $p[1] ]);
}
# xxx multi-.orig upstreams
return $unknown->("complex merge");
}
sub walk ($;$$);
sub walk {
my ($input,
$nogenerate,$report) = @_;
# => ($tip, $breakwater_tip)
# (or nothing, if $nogenerate)
# go through commits backwards
# we generate two lists of commits to apply:
# breakwater branch and upstream patches
my (@brw_cl, @upp_cl, @processed);
my %found;
my $upp_limit;
my @pseudomerges;
my $cl;
my $xmsg = sub {
my ($appendinfo) = @_;
my $ms = $cl->{Msg};
chomp $ms;
$ms .= "\n\n[git-debrebase $appendinfo]\n";
return (Msg => $ms);
};
my $rewrite_from_here = sub {
my $sp_cl = { SpecialMethod => 'StartRewrite' };
push @brw_cl, $sp_cl;
push @processed, $sp_cl;
};
my $cur = $input;
my $prdelim = "";
my $prprdelim = sub { print $report $prdelim if $report; $prdelim=""; };
my $prline = sub {
return unless $report;
print $report $prdelim, @_;
$prdelim = "\n";
};
my $bomb = sub { # usage: return $bomb->();
print $report " Unprocessable" if $report;
$prprdelim->();
if ($nogenerate) {
return (undef,undef);
}
die "commit $cur: Cannot cope with this commit";
};
for (;;) {
if (!defined $cur) {
push @brw_cl, { ExactlyParents => [] };
$prline->("Origin");
last;
}
$cl = classify $cur;
my $ty = $cl->{Type};
my $st = $cl->{SubType};
$prline->("$cl->{CommitId} $cl->{Type}");
$found{$ty. ( defined($st) ? "-$st" : '' )}++;
push @processed, $cl;
my $p0 = @{ $cl->{Parents} }==1 ? $cl->{Parents}[0]{CommitId} : undef;
if ($ty eq 'AddPatches') {
$cur = $p0;
$rewrite_from_here->();
next;
} elsif ($ty eq 'Packaging') {
push @brw_cl, $cl;
$cur = $p0;
next;
} elsif ($ty eq 'BreakwaterStart') {
push @brw_cl, { ExactlyParents => [$cur] };
last;
} elsif ($ty eq 'Upstream') {
push @upp_cl, $cl;
$cur = $p0;
next;
} elsif ($ty eq 'Mixed') {
my $queue = sub {
my ($q, $wh) = @_;
my $cls = { $cl, $xmsg->("split mixed commit: $wh part") };
push @$q, $cls;
};
$queue->(\@brw_cl, "debian");
$queue->(\@upp_cl, "upstream");
$rewrite_from_here->();
$cur = $p0;
next;
} elsif ($ty eq 'Pseudomerge') {
print $report " Contributor=$ty->{Contributor}" if $report;
push @pseudomerges, $cl;
$rewrite_from_here->();
$cur = $ty->{Contributor};
next;
} elsif ($ty eq 'BreakwaterUpstreamMerge') {
push @brw_cl, { ExactlyParents => [$cur] };
$prline->("PreviousBreakwater");
last;
} elsif ($ty eq 'DgitImportUnpatched') {
my $pm = $pseudomerges[-1];
if (defined $pm) {
# To an extent, this is heuristic. Imports don't have
# a useful history of the debian/ branch. We assume
# that the first pseudomerge after an import has a
# useful history of debian/, and ignore the histories
# from later pseudomerges. Often the first pseudomerge
# will be the dgit import of the upload to the actual
# suite intended by the non-dgit NMUer, and later
# pseudomerges may represent in-archive copies.
my $ovwrs = $pm->{Overwritten};
printf $report " PM=%s \@Overwr:%d", $pm, (scalar @$ovwrs)
if $report;
if (@$ovwrs != 1) {
return $bomb->();
}
my $ovwr = $ovwrs->[0]{CommitId};
printf $report " Overwr=%s", $ovwr if $report;
# This import has a tree which is just like a
# breakwater tree, but it has the wrong history. It
# ought to have the previous breakwater (which the
# pseudomerge overwrote) as an ancestor. That will
# make the history of the debian/ files correct. As
# for the upstream version: either it's the same as
# was ovewritten (ie, same as the previous
# breakwater), in which case that history is precisely
# right; or, otherwise, it was a non-gitish upload of a
# new upstream version. We can tell these apart by
# looking at the tree of the supposed upstream.
push @brw_cl, {
%$cl,
SpecialMethod => 'DgitImportDebianUpdate',
$xmsg->("convert dgit import: debian changes")
};
my $differs = (get_differs $ovwr, $cl->{Tree});
printf $report " Differs=%#x", $differs if $report;
if ($differs & D_UPS) {
printf $report " D_UPS" if $report;
# This will also trigger if a non-dgit git-based NMU
# deleted .gitignore (which is a thing that some of
# the existing git tools do if the user doesn't
# somehow tell them not to). Ah well.
push @brw_cl, {
%$cl,
SpecialMethod => 'DgitImportUpstreamUpdate',
$xmsg->("convert dgit import: upstream changes")
};
}
$prline->(" Import");
$rewrite_from_here->();
$upp_limit //= $#upp; # further, deeper, patches discarded
$cur = $ovwr;
next;
} else {
# Everything is from this import. This kind of import
# is already in valid breakwater format, with the
# patches as commits.
printf $report " NoPM" if $report;
$prline->(" ImportOrigin");
# last thing we processed will have been the first patch,
# if there is one; which is fine, so no need to rewrite
# on account of this import
push @brw_cl, { ExactlyParents => [$cur] };
last;
}
die "$ty ?";
} else {
return $bomb->();
}
}
$prprdelim->();
return if $nogenerate;
# Now we build it back up again
workarea_fresh();
my $rewriting = 0;
my $build = $basis;
my $rm_tree_cached = sub {
my ($subdir) = @_;
runcmd @git, qw(rm --quiet -rf --cached), $subdir;
};
my $read_tree_debian = sub {
my ($treeish) = @_;
$rm_tree_cached->(qw(debian));
runcmd @git, qw(read-tree --prefix=debian/), "$treeish:debian";
};
my $read_tree_upstream = sub {
my ($treeish) = @_;
runcmd @git, qw(read-tree), $treeish;
$read_tree_debian->($build);
};
my $committer_authline = calculate_committer_authline();
in_workarea sub {
mkdir $rd or $!==EEXIST or die $!;
my $current_method;
foreach my $cl (qw(Debian), (reverse @brw_cl),
{ SpecialMethod => 'RecordBreakwaterTip' },
qw(Upstream), (reverse @upp_cl)) {
if (!ref $cl) {
$current_method = $cl;
next;
}
my $method = $cl->{SpecialMethod} // $current_method;
my @parents = ($build);
my $cltree = $cl->{CommitId};
if ($method eq 'Debian') {
$read_tree_debian->($cltree);
} elsif ($method eq 'Upstream') {
$read_tree_upstream->($cltree);
} elsif ($method eq 'StartRewrite') {
$rewriting = 1;
next;
} elsif ($method eq 'RecordBreakwaterTip') {
last if $wantbrwonly;
$breakwater = $build;
next;
} elsif ($method eq 'DgitImportDebianUpdate') {
$read_tree_debian->($cltree);
$rm_tree_cached->(qw(debian/patches));
} elsif ($method eq 'DgitImportUpstreamUpdate') {
$read_tree_upstream->($cltree);
push @parents, map { $_->{CommitId} } @{ $cl->{OrigParents} };
} else {
confess "$method ?";
}
$rewriting ||= $cl ne pop @processed;
my $newtree = cmdoutput @git, qw(write-tree);
my $ch = $cl->{Hdr};
$ch =~ s{^tree .*}{tree $newtree}m or confess "$ch ?";
$ch =~ s{^parent .*\n}{}m;
$ch =~ s{(?=^author)}{
map { "parent $_\n" } @parents
}me or confess "$ch ?";
if ($rewriting) {
$ch =~ s{^committer .*$}{$committer_authline}m
or confess "$ch ?";
}
my $cf = "$rd/m$rewriting";
open CD, ">", $cf or die $!;
print CD $ch, "\n", $cl->{Msg} or die $!;
close CD or die $!;
my @cmd = (@git, qw(hash-object));
push @cmd, qw(-w) if $rewriting;
push @cmd, qw(-t commit), $cf;
my $newcommit = cmdoutput @cmd;
confess "$ch ?" unless $rewriting or $newcommit eq $cl->{CommitId};
$build = $newcommit;
}
};
runcmd @git, qw(diff-tree --quiet),
map { $wantdebonly ? "$_:debian" : $_ }
$input, $build;
return ($build, $breakwater);
}
sub get_head () { return git_rev_parse qw(HEAD); }
sub update_head ($$) {
my ($old, $new, $mrest) = @_;
runcmd @git, qw(update-ref -m), "git-debrebase $mrest", $new, $old;
}
sub cmd_launder () {
badusage "no arguments to launder allowed";
my $old = get_head();
my ($tip,$breakwater) = walk $old;
update_head $old, $tip, 'launder';
# no tree changes except debian/patches
runcmd @git, qw(rm --quiet -rf debian/patches);
printf "# breakwater tip\n%s\n", $breakwater;
}
sub cmd_analyse () {
die if ($ARGV[0]//'') =~ m/^-/;
badusage "too many arguments to analyse" if @ARGV>1;
my ($old) = @ARGV;
if (defined $old) {
$old = git_rev_parse $old;
} else {
$old = get_head();
}
my ($dummy,$breakwater) = walk $old, 1,*STDOUT;
print "$breakwater BREAKWATER\n";
STDOUT->error and die $!;
}
my $toplevel = runcmd @git, qw(rev-parse --show-toplevel);
chdir $toplevel or die "chdir $toplevel: $!";
my $cmd = shift @ARGV;
my $cmdfn = $cmd;
$cmdfn =~ y/-/_/;
$cmdfn = ${*::}{"cmd_$cmdfn"};
$cmdfn or badusage "unknown git-debrebase sub-operation $cmd";
$cmdfn->();