X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=dgit.git;a=blobdiff_plain;f=git-debrebase;h=2c7828d1101edd4c6c98aa31b56cb560f6d1c9af;hp=bee0249753880600bfd2f7834bde3126ed3fecb5;hb=7ec31b1b534340f4d5688c7862d1b95c11964059;hpb=8d7ae3032f607936deb0b63109b710eb4381aa55

diff --git a/git-debrebase b/git-debrebase
index bee02497..2c7828d1 100755
--- a/git-debrebase
+++ b/git-debrebase
@@ -21,6 +21,7 @@
 END { $? = $Debian::Dgit::ExitStatus::desired // -1; };
 use Debian::Dgit::GDR;
 use Debian::Dgit::ExitStatus;
+use Debian::Dgit::I18n;
 
 use strict;
 
@@ -30,6 +31,7 @@ setup_sigwarn();
 use Memoize;
 use Carp;
 use POSIX;
+use Locale::gettext;
 use Data::Dumper;
 use Getopt::Long qw(:config posix_default gnu_compat bundling);
 use Dpkg::Version;
@@ -38,7 +40,7 @@ use File::Copy;
 
 $debugcmd_when_debuglevel = 2;
 
-our ($usage_message) = <<'END';
+our ($usage_message) = i_ <<'END';
 usages:
   git-debrebase [<options>] [--|-i <git rebase options...>]
   git-debrebase [<options>] status
@@ -50,11 +52,9 @@ usages:
 See git-debrebase(1), git-debrebase(5), dgit-maint-debrebase(7) (in dgit).
 END
 
-our ($opt_force, $opt_careful, $opt_noop_ok, @opt_anchors);
+our ($opt_force, $opt_noop_ok, $opt_merges, @opt_anchors);
 our ($opt_defaultcmd_interactive);
 
-$opt_careful = 0;
-
 our $us = qw(git-debrebase);
 
 our $wrecknoteprefix = 'refs/debrebase/wreckage';
@@ -64,7 +64,7 @@ $|=1;
 
 sub badusage ($) {
     my ($m) = @_;
-    print STDERR "$us: bad usage: $m\n";
+    print STDERR f_ "%s: bad usage: %s\n", $us, $m;
     finish 8;
 }
 
@@ -75,7 +75,7 @@ sub getoptions_main {
 }
 sub getoptions {
     my $sc = shift;
-    getoptions_main "bad options follow \`git-debrebase $sc'", @_;
+    getoptions_main +(f_ "bad options follow \`git-debrebase %s'", $sc), @_;
 }
 
 sub cfg ($;$) {
@@ -86,7 +86,7 @@ sub cfg ($;$) {
     push @cmd, $k;
     my $out = cmdoutput_errok @cmd;
     if (!defined $out) {
-	fail "missing required git config $k" unless $optional;
+	fail f_ "missing required git config %s", $k unless $optional;
 	return ();
     }
     my @l = split /\0/, $out;
@@ -105,7 +105,7 @@ sub dd ($) {
 sub get_commit ($) {
     my ($objid) = @_;
     my $data = (git_cat_file $objid, 'commit');
-    $data =~ m/(?<=\n)\n/ or die "$objid ($data) ?";
+    $data =~ m/(?<=\n)\n/ or confess "$objid ($data) ?";
     return ($`,$');
 }
 
@@ -144,10 +144,10 @@ sub run_ref_updates_now ($$) {
 
     my @upd_cmd = (git_update_ref_cmd "debrebase: $mrest", qw(--stdin));
     debugcmd '>|', @upd_cmd;
-    open U, "|-", @upd_cmd or die $!;
+    open U, "|-", @upd_cmd or confess $!;
     foreach (@$updates) {
 	printdebug ">= ", $_, "\n";
-	print U $_, "\n" or die $!;
+	print U $_, "\n" or confess $!;
     }
     printdebug ">\$\n";
     close U or failedcmd @upd_cmd;
@@ -173,7 +173,8 @@ sub all_snags_summarised () {
 sub run_deferred_updates ($) {
     my ($mrest) = @_;
 
-    confess 'dangerous internal error' unless all_snags_summarised();
+    my $m = 'dangerous internal error';
+    confess $m.' - '.__ $m unless all_snags_summarised();
 
     merge_wreckage_cleaning \@deferred_updates;
     run_ref_updates_now $mrest, \@deferred_updates;
@@ -198,8 +199,12 @@ sub get_tree ($;$$) {
 	return () if $type eq 'missing';
     }
 
+    $recurse = !!$recurse;
+
+    confess "get_tree needs object not $x ?" unless $x =~ m{^[0-9a-f]+\:};
+
     our (@get_tree_memo, %get_tree_memo);
-    my $memo = $get_tree_memo{$x};
+    my $memo = $get_tree_memo{$recurse,$x};
     return @$memo if $memo;
 
     local $Debian::Dgit::debugcmd_when_debuglevel = 3;
@@ -216,7 +221,7 @@ sub get_tree ($;$$) {
 	push @l, [ $n, $i ];
 	confess "$x need $last < $n ?" unless $last lt $n;
     }
-    $get_tree_memo{$x} = \@l;
+    $get_tree_memo{$recurse,$x} = \@l;
     push @get_tree_memo, $x;
     if (@get_tree_memo > 10) {
 	delete $get_tree_memo{ shift @get_tree_memo };
@@ -225,15 +230,18 @@ sub get_tree ($;$$) {
 }
 
 sub trees_diff_walk ($$$;$) {
-    # trees_diff_walk [$all,] $x, $y, sub {... }
-    # calls sub->($name, $ix, $iy) for each difference (with $all, each name)
+    # trees_diff_walk [{..opts...},] $x, $y, sub {... }
+    # calls sub->($name, $ix, $iy) for each difference
     # $x and $y are as for get_tree
     # where $name, $ix, $iy are $name and $info from get_tree
-    my $all = shift @_ if @_>=4;
+    # opts are   all       call even for names same in both
+    #            recurse   call even for names same in both
+    my $opts = shift @_ if @_>=4;
     my ($x,$y,$call) = @_;
+    my $all = $opts->{all};
     return if !$all and $x eq $y;
-    my @x = get_tree $x;
-    my @y = get_tree $y;
+    my @x = get_tree $x, 0, $opts->{recurse};
+    my @y = get_tree $y, 0, $opts->{recurse};
     printdebug "trees_diff_walk(..$x,$y..) ".Dumper(\@x,\@y)
 	if $debuglevel >= 3;
     while (@x || @y) {
@@ -305,13 +313,16 @@ sub get_differs ($$) {
 
 	    my $xp = $ix && "$xd/patches";
 	    my $yp = $iy && "$yd/patches";
-	    trees_diff_walk $xp, $yp, sub {
+	    trees_diff_walk { recurse=>1 }, $xp, $yp, sub {
 		my ($n,$ix,$iy) = @_;
 
 		# analyse difference in debian/patches
 
 		my $ok;
-		if ($n !~ m/\.series$/s && !$ix && $plain->($iy)) {
+		if ($n =~ m{/$}s) {
+		    # we are recursing; directories may appear and disappear
+		    $ok = 1;
+		} elsif ($n !~ m/\.series$/s && !$ix && $plain->($iy)) {
 		    $ok = 1;
 		} elsif ($n eq 'series' && $plain->($ix) && $plain->($iy)) {
 		    my $x_s = (git_cat_file "$xp/series", 'blob');
@@ -387,10 +398,10 @@ sub snag ($$;@) {
     my ($tag,$msg) = @_; # ignores extra args, for benefit of keycommits
     if (grep { $_ eq $tag } @snag_force_opts) {
 	$snags_forced++;
-	print STDERR "git-debrebase: snag ignored (-f$tag): $msg\n";
+	print STDERR f_ "%s: snag ignored (-f%s): %s\n", $us, $tag, $msg;
     } else {
 	$snags_tripped++;
-	print STDERR "git-debrebase: snag detected (-f$tag): $msg\n";
+	print STDERR f_ "%s: snag detected (-f%s): %s\n", $us, $tag, $msg;
     }
 }
 
@@ -402,17 +413,17 @@ sub snag ($$;@) {
 sub snags_maybe_bail () {
     return if all_snags_summarised();
     if ($snags_forced) {
-	printf STDERR
+	print STDERR f_
 	    "%s: snags: %d overriden by individual -f options\n",
 	    $us, $snags_forced;
     }
     if ($snags_tripped) {
 	if ($opt_force) {
-	    printf STDERR
+	    print STDERR f_
 		"%s: snags: %d overriden by global --force\n",
 		$us, $snags_tripped;
 	} else {
-	    fail sprintf
+	    fail f_
   "%s: snags: %d blocker(s) (you could -f<tag>, or --force)",
 		$us, $snags_tripped;
 	}
@@ -428,11 +439,65 @@ sub any_snags () {
     return $snags_forced || $snags_tripped;
 }
 
+sub ffq_prev_branchinfo () {
+    my $current = git_get_symref();
+    return gdr_ffq_prev_branchinfo($current);
+}
+
+sub record_gdrlast ($$;$) {
+    my ($gdrlast, $newvalue, $oldvalue) = @_;
+    $oldvalue ||= $git_null_obj;
+    push @deferred_updates, "update $gdrlast $newvalue $oldvalue";
+}
+
+sub fail_unprocessable ($) {
+    my ($msg) = @_;
+    changedir $maindir;
+    my ($ffqs, $ffqm, $symref, $ffq_prev, $gdrlast) = ffq_prev_branchinfo();
+
+    my $mangled = __ <<END;
+Branch/history seems mangled - no longer in gdr format.
+See ILLEGAL OPERATIONS in git-debrebase(5).
+END
+    chomp $mangled;
+
+    if (defined $ffqm) {
+	fail f_ <<END, $msg, $ffqm;
+%s
+Is this meant to be a gdr branch?  %s
+END
+    } elsif (git_get_ref $ffq_prev) {
+	fail f_ <<END, $msg, $mangled;
+%s
+%s
+Consider git-debrebase scrap, to throw away your recent work.
+END
+    } elsif (!git_get_ref $gdrlast) {
+	fail f_ <<END, $msg;
+%s
+Branch does not seem to be meant to be a git-debrebase branch?
+Wrong branch, or maybe you needed git-debrebase convert-from-*.
+END
+    } elsif (is_fast_fwd $gdrlast, git_rev_parse 'HEAD') {
+	fail <<END;
+$msg
+$mangled
+END
+    } else {
+	fail f_ <<END, $msg;
+%s
+Branch/history mangled, and diverged since last git-debrebase.
+Maybe you reset to, or rebased from, somewhere inappropriate.
+END
+    }
+};
+
 sub gbp_pq_export ($$$) {
     my ($bname, $base, $tip) = @_;
     # must be run in a workarea.  $bname and patch-queue/$bname
     # ought not to exist.  Leaves you on patch-queue/$bname with
     # the patches staged but not committed.
+    # returns 1 if there were any patches
     printdebug "gbp_pq_export $bname $base $tip\n";
     runcmd @git, qw(checkout -q -b), $bname, $base;
     runcmd @git, qw(checkout -q -b), "patch-queue/$bname", $tip;
@@ -442,7 +507,9 @@ sub gbp_pq_export ($$$) {
 	{ local ($!,$?); copy('../gbp-pq-err', \*STDERR); }
 	failedcmd @gbp_cmd;
     }
-    runcmd @git, qw(add -f debian/patches) if stat_exists 'debian/patches';
+    return 0 unless stat_exists 'debian/patches';
+    runcmd @git, qw(add -f debian/patches);
+    return 1;
 }
 
 
@@ -539,22 +606,21 @@ sub merge_series ($$$;@) {
 	playtree_setup();
 	foreach my $q ($base_q, reverse @input_qs) {
 	    my $s = $q->{MR}{S};
-	    gbp_pq_export "p-$s", $q->{SeriesBase}, $q->{SeriesTip};
+	    my $any = gbp_pq_export "p-$s", $q->{SeriesBase}, $q->{SeriesTip};
 	    my @earlier;
-	    if (open S, $seriesfile) {
+	    if ($any) {
+		open S, $seriesfile or confess "$seriesfile $!";
 		while (my $patch = <S>) {
-		    chomp $patch or die $!;
+		    chomp $patch or confess $!;
 		    $prereq{$patch} //= {};
 		    foreach my $earlier (@earlier) {
-			$prereq{$patch}{$earlier}{$s}++ and die;
+			$prereq{$patch}{$earlier}{$s}++ and confess;
 		    }
 		    push @earlier, $patch;
-		    stat "debian/patches/$patch" or die "$patch ?";
+		    stat "debian/patches/$patch" or confess "$patch ?";
 		}
-		S->error and die "$seriesfile $!";
+		S->error and confess "$seriesfile $!";
 		close S;
-	    } else {
-		die "$seriesfile $!" unless $!==ENOENT;
 	    }
 	    read_tree_upstream $newbase, 1;
 	    my $pec = make_commit [ grep { defined } $base_q->{MR}{PEC} ], [
@@ -632,7 +698,7 @@ sub merge_series ($$$;@) {
 	my $authordate = sub {
 	    my ($f) = @_;
 	    $authordate{$f} //= do {
-		open PF, "<", "debian/patches/$f" or die "$f $!";
+		open PF, "<", "debian/patches/$f" or confess "$f $!";
 		while (<PF>) {
 		    return $nodate if m/^$/;
 		    last if s{^Date: }{};
@@ -642,7 +708,7 @@ sub merge_series ($$$;@) {
 	    };
 	};
 
-	open NS, '>', $seriesfile or die $!;
+	open NS, '>', $seriesfile or confess $!;
 
 	while (keys %prereq) {
 	    my $best;
@@ -657,7 +723,7 @@ sub merge_series ($$$;@) {
 		$best = $try;
 	    }
 	    printdebug "merge_series series next $best\n";
-	    print NS "$best\n" or die $!;
+	    print NS "$best\n" or confess $!;
 	    delete $prereq{$best};
 	    foreach my $gp (values %prereq) {
 		delete $gp->{$best};
@@ -683,6 +749,8 @@ sub merge_series_patchqueue_convert ($$$) {
 	runcmd @git, qw(checkout -q -b mergec), $merged_pq;
 
 	merge_attempt_cmd($wrecknotes, qw(gbp pq import));
+	# MERGE-TODO consider git-format-patch etc. instead,
+	# since gbp pq doesn't always round-trip :-/
 
 	# OK now we are on patch-queue/merge, and we need to rebase
 	# onto the intended parent and drop the patches from each one
@@ -697,9 +765,9 @@ sub merge_series_patchqueue_convert ($$$) {
 	    my $tree = cmdoutput @git, qw(write-tree);
 	    $commit =~ s{^parent (\S+)$}{parent $build}m or confess;
 	    $commit =~ s{^tree (\S+)$}{tree $tree}m      or confess;
-	    open C, ">", "../mcommit" or die $!;
-	    print C $commit or die $!;
-	    close C or die $!;
+	    open C, ">", "../mcommit" or confess $!;
+	    print C $commit or confess $!;
+	    close C or confess $!;
 	    $build = cmdoutput @git, qw(hash-object -w -t commit ../mcommit);
 	}
 	$result = $build;
@@ -770,11 +838,11 @@ sub parsecommit ($;$) {
     #    $p_ref, if provided, must be [] and is used as a base for Parents
 
     $p_ref //= [];
-    die if @$p_ref;
+    confess if @$p_ref;
 
     my ($h,$m) = get_commit $objid;
 
-    my ($t) = $h =~ m/^tree (\w+)$/m or die $objid;
+    my ($t) = $h =~ m/^tree (\w+)$/m or confess $objid;
     my (@ph) = $h =~ m/^parent (\w+)$/mg;
 
     my $r = {
@@ -863,9 +931,11 @@ sub classify ($) {
 	# reject it here then we avoid making the pseudomerge which
 	# would be needed to push it.
 
-	my $badanchor = sub { $unknown->("git-debrebase \`anchor' but @_"); };
-	@p == 2 or return $badanchor->("has other than two parents");
-	$haspatches and return $badanchor->("contains debian/patches");
+	my $badanchor = sub {
+	    $unknown->(f_ "git-debrebase \`anchor' but %s", "@_");
+	};
+	@p == 2 or return $badanchor->(__ "has other than two parents");
+	$haspatches and return $badanchor->(__ "contains debian/patches");
 
 	# How to decide about l/r ordering of anchors ?  git
 	# --topo-order prefers to expand 2nd parent first.  There's
@@ -891,11 +961,11 @@ sub classify ($) {
 	# parents from left to right, in order, so it's easy to see
 	# which way round a pseudomerge is.
 
-	$p[0]{IsOrigin} and $badanchor->("is an origin commit");
+	$p[0]{IsOrigin} and $badanchor->(__ "is an origin commit");
 	$p[1]{Differs} & ~DS_DEB and
-	    $badanchor->("upstream files differ from left parent");
+	    $badanchor->(__ "upstream files differ from left parent");
 	$p[0]{Differs} & ~D_UPS and
-	    $badanchor->("debian/ differs from right parent");
+	    $badanchor->(__ "debian/ differs from right parent");
 
 	return $classify->(qw(Anchor),
 			   OrigParents => [ $p[1] ]);
@@ -906,7 +976,7 @@ sub classify ($) {
 	if ($d == D_PAT_ADD) {
 	    return $classify->(qw(AddPatches));
 	} elsif ($d & (D_PAT_ADD|D_PAT_OTH)) {
-	    return $unknown->("edits debian/patches");
+	    return $unknown->(__ "edits debian/patches");
 	} elsif ($d & DS_DEB and !($d & ~DS_DEB)) {
 	    my ($ty,$dummy) = git_cat_file "$p[0]{CommitId}:debian";
 	    if ($ty eq 'tree') {
@@ -918,20 +988,20 @@ sub classify ($) {
 	    } elsif ($ty eq 'missing') {
 		return $classify->(qw(BreakwaterStart));
 	    } else {
-		return $unknown->("parent's debian is not a directory");
+		return $unknown->(__ "parent's debian is not a directory");
 	    }
 	} elsif ($d == D_UPS) {
 	    return $classify->(qw(Upstream));
 	} elsif ($d & DS_DEB and $d & D_UPS and !($d & ~(DS_DEB|D_UPS))) {
 	    return $classify->(qw(Mixed));
 	} elsif ($d == 0) {
-	    return $unknown->("no changes");
+	    return $unknown->(__ "no changes");
 	} else {
 	    confess "internal error $objid ?";
 	}
     }
     if (!@p) {
-	return $unknown->("origin commit");
+	return $unknown->(__ "origin commit");
     }
 
     if (@p == 2 && @identical == 1) {
@@ -944,7 +1014,8 @@ sub classify ($) {
     if (@p == 2 && @identical == 2) {
 	my $get_t = sub {
 	    my ($ph,$pm) = get_commit $_[0]{CommitId};
-	    $ph =~ m/^committer .* (\d+) [-+]\d+$/m or die "$_->{CommitId} ?";
+	    $ph =~ m/^committer .* (\d+) [-+]\d+$/m
+		or confess "$_->{CommitId} ?";
 	    $1;
 	};
 	my @bytime = @p;
@@ -981,14 +1052,14 @@ sub classify ($) {
 	return $classify->("MergedBreakwaters");
     }
     if ($r->{Msg} =~ m{^\[(git-debrebase|dgit)[: ].*\]$}m) {
-	return $unknown->("unknown kind of merge from $1");
+	return $unknown->(f_ "unknown kind of merge from %s", $1);
     }
     if (@p > 2) {
-	return $unknown->("octopus merge");
+	return $unknown->(__ "octopus merge");
     }
 
-    if (!$ENV{GIT_DEBREBASE_EXPERIMENTAL_MERGE}) {
-	return $unknown->("general two-parent merge");
+    if (!$opt_merges) {
+	return $unknown->(__ "general two-parent merge");
     }
 
     return $classify->("VanillaMerge");
@@ -1005,7 +1076,8 @@ sub mergedbreakwaters_anchor ($) {
 	$best_anchor = $panchor
 	    if !defined $best_anchor
 	    or is_fast_fwd $best_anchor, $panchor;
-	fail "inconsistent anchors in merged-breakwaters $p->{CommitId}"
+	fail f_ "inconsistent anchors in merged-breakwaters %s",
+	    $p->{CommitId}
 	    unless is_fast_fwd $panchor, $best_anchor;
     }
     return $best_anchor;
@@ -1015,9 +1087,8 @@ sub keycommits ($;$$$$$) {
     my ($head, $furniture, $unclean, $trouble, $fatal, $claimed_bw) = @_;
     # => ($anchor, $breakwater)
 
-    # $unclean->("unclean-$tagsfx", $msg, $cl)
     # $furniture->("unclean-$tagsfx", $msg, $cl)
-    # $dgitimport->("unclean-$tagsfx", $msg, $cl))
+    # $unclean->("unclean-$tagsfx", $msg, $cl)
     #   is callled for each situation or commit that
     #   wouldn't be found in a laundered branch
     # $furniture is for furniture commits such as might be found on an
@@ -1041,11 +1112,11 @@ sub keycommits ($;$$$$$) {
     my $clogonly;
     my $cl;
     my $found_pm;
-    $fatal //= sub { fail $_[1]; };
+    $fatal //= sub { fail_unprocessable $_[1]; };
     my $x = sub {
 	my ($cb, $tagsfx, $mainwhy, $xwhy) = @_;
 	my $why = $mainwhy.$xwhy;
-	my $m = "branch needs laundering (run git-debrebase): $why";
+	my $m = f_ "branch needs laundering (run git-debrebase): %s", $why;
 	fail $m unless defined $cb;
 	return unless $cb;
 	$cb->("unclean-$tagsfx", $why, $cl, $mainwhy);
@@ -1073,41 +1144,47 @@ sub keycommits ($;$$$$$) {
 	    $found_anchor->($head);
 	} elsif ($ty eq 'Upstream') {
 	    $x->($unclean, 'ordering',
- "packaging change ($breakwater) follows upstream change"," (eg $head)")
+ (f_ "packaging change (%s) follows upstream change", $breakwater),
+		 (f_ " (eg %s)", $head))
 		if defined $breakwater;
 	    $clogonly = undef;
 	    $breakwater = undef;
 	} elsif ($ty eq 'Mixed') {
 	    $x->($unclean, 'mixed',
-		 "found mixed upstream/packaging commit"," ($head)");
+		 (__ "found mixed upstream/packaging commit"),
+		 (f_ " (%s)", $head));
 	    $clogonly = undef;
 	    $breakwater = undef;
 	} elsif ($ty eq 'Pseudomerge' or
 		 $ty eq 'AddPatches') {
 	    my $found_pm = 1;
 	    $x->($furniture, (lc $ty),
-		 "found interchange bureaucracy commit ($ty)"," ($head)");
+		 (f_ "found interchange bureaucracy commit (%s)", $ty),
+		 (f_ " (%s)", $head));
 	} elsif ($ty eq 'DgitImportUnpatched') {
 	    if ($found_pm) {
 		$x->($trouble, 'dgitimport',
-		     "found dgit dsc import"," ($head)");
+		     (__ "found dgit dsc import"),
+		     (f_ " (%s)", $head));
 		return (undef,undef);
 	    } else {
 		$x->($fatal, 'unprocessable',
-		     "found bare dgit dsc import with no prior history",
-		     " ($head)");
+		     (__ "found bare dgit dsc import with no prior history"),
+		     (f_ " (%s)", $head));
 		return (undef,undef);
 	    }
 	} elsif ($ty eq 'VanillaMerge') {
 	    $x->($trouble, 'vanillamerge',
-		 "found vanilla merge"," ($head)");
+		 (__ "found vanilla merge"),
+		 (f_ " (%s)", $head));
 	    return (undef,undef);
 	} elsif ($ty eq 'MergedBreakwaters') {
 	    $found_anchor->(mergedbreakwaters_anchor $cl);
 	} else {
 	    $x->($fatal, 'unprocessable',
-		 "found unprocessable commit, cannot cope: $cl->{Why}",
-		 " ($head)");
+		 (f_ "found unprocessable commit, cannot cope: %s",
+		     $cl->{Why}),
+		 (f_ " (%s)", $head));
 	    return (undef,undef);
 	}
 	$head = $cl->{Parents}[0]{CommitId};
@@ -1138,8 +1215,8 @@ sub walk ($;$$$) {
 	my ($prose, $info) = @_;
 	my $ms = $cl->{Msg};
 	chomp $ms;
-	$info //= '';
-	$ms .= "\n\n[git-debrebase$info: $prose]\n";
+	confess unless defined $info;
+	$ms .= "\n\n[git-debrebase $info: $prose]\n";
 	return (Msg => $ms);
     };
     my $rewrite_from_here = sub {
@@ -1166,12 +1243,14 @@ sub walk ($;$$$) {
 	if ($nogenerate) {
 	    return (undef,undef);
 	}
-	fail "found unprocessable commit, cannot cope".
-	    (defined $cl->{Why} ? "; $cl->{Why}:": ':').
-	    " (commit $cur) (d.".
-	    (join ' ', map { sprintf "%#x", $_->{Differs} }
-	     @{ $cl->{Parents} }).
-		 ")";
+	my $d =
+	    join ' ',
+	    map { sprintf "%#x", $_->{Differs} }
+	    @{ $cl->{Parents} };
+	fail_unprocessable sprintf +(defined $cl->{Why}
+ ? 'found unprocessable commit, cannot cope; %3$s: (commit %1$s) (d.%2$s)'
+ : 'found unprocessable commit, cannot cope: (commit %1$s) (d.%2$s)'),
+                                   $cur, $d, $cl->{Why};
     };
 
     my $build;
@@ -1220,7 +1299,7 @@ sub walk ($;$$$) {
 	} elsif ($ty eq 'Mixed') {
 	    my $queue = sub {
 		my ($q, $wh) = @_;
-		my $cls = { %$cl, $xmsg->("split mixed commit: $wh part") };
+		my $cls = { %$cl, $xmsg->("mixed commit: $wh part",'split') };
 		push @$q, $cls;
 	    };
 	    $queue->(\@brw_cl, "debian");
@@ -1273,12 +1352,12 @@ sub walk ($;$$$) {
 		push @brw_cl, {
 		    %$cl,
 		    SpecialMethod => 'DgitImportDebianUpdate',
-                    $xmsg->("convert dgit import: debian changes")
+                    $xmsg->("debian changes", 'convert dgit import')
 		}, {
 		    %$cl,
 		    SpecialMethod => 'DgitImportUpstreamUpdate',
                     $xmsg->("convert dgit import: upstream update",
-			    " anchor")
+			    "anchor")
 		};
 		$prline->(" Import");
 		$rewrite_from_here->(\@brw_cl);
@@ -1294,7 +1373,7 @@ sub walk ($;$$$) {
 		$cl->{Why} = "bare dgit dsc import";
 		return $bomb->();
 	    }
-	    die "$ty ?";
+	    confess "$ty ?";
 	} elsif ($ty eq 'MergedBreakwaters') {
 	    $last_anchor = mergedbreakwaters_anchor $cl;
 	    $build_start->(' MergedBreakwaters', $cur);
@@ -1471,7 +1550,7 @@ sub walk ($;$$$) {
                 %$cl,
                 SpecialMethod => 'MergeCreateMergedBreakwaters',
                 $xmsg->('constructed from vanilla merge',
-			' merged-breakwater'),
+			'merged-breakwater'),
             };
 	    push @upp_cl, {
                 %$cl,
@@ -1505,7 +1584,7 @@ sub walk ($;$$$) {
     confess "internal error" unless $build eq (pop @processed)->{CommitId};
 
     in_workarea sub {
-	mkdir $rd or $!==EEXIST or die $!;
+	mkdir $rd or $!==EEXIST or confess $!;
 	my $current_method;
 	my $want_debian = $build;
 	my $want_upstream = $build;
@@ -1600,7 +1679,7 @@ sub walk ($;$$$) {
 		    printdebug "WALK REWRITING NOW cl=$cl procd=$procd\n";
 		}
 	    }
-	    if ($rewriting || $opt_careful) {
+	    if ($rewriting) {
 		read_tree_upstream $want_upstream, 0, $want_debian;
 
 		my $newtree = cmdoutput @git, qw(write-tree);
@@ -1615,9 +1694,9 @@ sub walk ($;$$$) {
 			or confess "$ch ?";
 		}
 		my $cf = "$rd/m$rewriting";
-		open CD, ">", $cf or die $!;
-		print CD $ch, "\n", $cl->{Msg} or die $!;
-		close CD or die $!;
+		open CD, ">", $cf or confess $!;
+		print CD $ch, "\n", $cl->{Msg} or confess $!;
+		close CD or confess $!;
 		my @cmd = (@git, qw(hash-object));
 		push @cmd, qw(-w) if $rewriting;
 		push @cmd, qw(-t commit), $cf;
@@ -1647,7 +1726,7 @@ sub walk ($;$$$) {
     };
 
     my $final_check = get_differs $build, $input;
-    die sprintf "internal error %#x %s %s", $final_check, $input, $build
+    confess sprintf "internal error %#x %s %s", $final_check, $input, $build
 	if $final_check & ~D_PAT_ADD;
 
     my @r = ($build, $breakwater, $last_anchor);
@@ -1675,7 +1754,7 @@ sub update_head_checkout ($$$) {
 sub update_head_postlaunder ($$$) {
     my ($old, $tip, $reflogmsg) = @_;
     return if $tip eq $old && !@deferred_updates;
-    print "git-debrebase: laundered (head was $old)\n";
+    print "$us: laundered (head was $old)\n";
     update_head $old, $tip, $reflogmsg;
     # no tree changes except debian/patches
     runcmd @git, qw(rm --quiet --ignore-unmatch -rf debian/patches);
@@ -1730,12 +1809,7 @@ sub cmd_analyse () {
 	$old = git_rev_parse 'HEAD';
     }
     my ($dummy,$breakwater) = walk $old, 1,*STDOUT;
-    STDOUT->error and die $!;
-}
-
-sub ffq_prev_branchinfo () {
-    my $current = git_get_symref();
-    return gdr_ffq_prev_branchinfo($current);
+    STDOUT->error and confess $!;
 }
 
 sub ffq_check ($;$$) {
@@ -1752,7 +1826,7 @@ sub ffq_check ($;$$) {
     # normally $currentval should be HEAD
     my ($currentval, $ff, $notff) =@_;
 
-    $ff //= sub { print $_[0] or die $!; };
+    $ff //= sub { print $_[0] or confess $!; };
     $notff //= \&snag;
 
     my ($status, $message, $current, $ffq_prev, $gdrlast)
@@ -1879,8 +1953,7 @@ sub stitch ($$$$$) {
 	    # ffq-prev is ahead of us, and the only tree changes it has
 	    # are possibly addition of things in debian/patches/.
 	    # Just wind forwards rather than making a pointless pseudomerge.
-	    push @deferred_updates,
-		"update $gdrlast $ffq_prev_commitish $git_null_obj";
+	    record_gdrlast $gdrlast, $ffq_prev_commitish;
 	    update_head_checkout $old_head, $ffq_prev_commitish,
 		"stitch (fast forward)";
 	    return;
@@ -1893,7 +1966,7 @@ sub stitch ($$$$$) {
 	'Declare fast forward / record previous work',
         "[git-debrebase pseudomerge: $prose]",
     ];
-    push @deferred_updates, "update $gdrlast $new_head $git_null_obj";
+    record_gdrlast $gdrlast, $new_head;
     update_head $old_head, $new_head, "stitch: $prose";
 }
 
@@ -1992,7 +2065,7 @@ sub cmd_new_upstream () {
             unless @ARGV && $ARGV[0] !~ m{^-};
 
 	my $c = git_rev_parse shift @ARGV;
-	die unless $n =~ m/^$extra_orig_namepart_re$/;
+	confess unless $n =~ m/^$extra_orig_namepart_re$/;
 	$newpiece->($n, New => $c);
     }
 
@@ -2006,7 +2079,7 @@ sub cmd_new_upstream () {
     my $old_upstream;
     if (!$old_anchor_cl->{OrigParents}) {
 	snag 'anchor-treated',
-	    'old anchor is recognised due to --anchor, cannot check upstream';
+ __ 'old anchor is recognised due to --anchor, cannot check upstream';
     } else {
 	$old_upstream = parsecommit
 	    $old_anchor_cl->{OrigParents}[0]{CommitId};
@@ -2112,36 +2185,45 @@ sub cmd_new_upstream () {
  "[git-debrebase anchor: new upstream $new_upstream_version, merge]",
             ];
 
-	my $clogsignoff = cmdoutput qw(git show),
-	    '--pretty=format:%an <%ae>  %aD',
-	    $new_bw;
-
 	# Now we have to add a changelog stanza so the Debian version
-	# is right.
-	die if unlink "debian";
-	die $! unless $!==ENOENT or $!==ENOTEMPTY;
-	unlink "debian/changelog" or $!==ENOENT or die $!;
-        mkdir "debian" or die $!;
-	open CN, ">", "debian/changelog" or die $!;
-	my $oldclog = git_cat_file ":debian/changelog";
-	$oldclog =~ m/^($package_re) \(\S+\) / or
-	    fail "cannot parse old changelog to get package name";
-	my $p = $1;
-	print CN <<END, $oldclog or die $!;
-$p ($new_version) UNRELEASED; urgency=medium
-
-  * Update to new upstream version $new_upstream_version.
-
- -- $clogsignoff
-
-END
-	close CN or die $!;
+	# is right.  We use debchange to do this.  Invoking debchange
+	# here is a bit fiddly because it has a lot of optional
+	# exciting behaviours, some of which will break stuff, and
+	# some of which won't work in a playtree.
+
+	# Make debchange use git's idea of the user's identity.
+	# That way, if the user never uses debchange et al, configuring
+	# git is enough.
+	my $usetup = sub {
+	    my ($e, $k) = @_;
+	    my $v = cfg $k, 1;
+	    defined $v or return;
+	    $ENV{$e} = $v;
+	};
+	$usetup->('DEBEMAIL',    'user.email');
+	$usetup->('DEBFULLNAME', 'user.name');
+
+sleep 2;
+
+	my @dch = (qw(debchange
+		      --allow-lower-version .*
+		      --no-auto-nmu
+		      --preserve
+		      --vendor=Unknown-Vendor
+		      --changelog debian/changelog
+		      --check-dirname-level 0
+		      --release-heuristic=changelog
+		      -v), $new_version,
+		   "Update to new upstream version $new_upstream_version.");
+
+	runcmd @git, qw(checkout -q debian/changelog);
+	runcmd @dch;
 	runcmd @git, qw(update-index --add --replace), 'debian/changelog';
 
 	# Now we have the final new breakwater branch in the index
         $new_bw = make_commit [ $new_bw ],
             [ "Update changelog for new upstream $new_upstream_version",
-              "[git-debrebase: new upstream $new_upstream_version, changelog]",
+              "[git-debrebase changelog: new upstream $new_upstream_version]",
             ];
     };
 
@@ -2163,7 +2245,7 @@ sub cmd_record_ffq_prev () {
     badusage "no arguments allowed" if @ARGV;
     my ($status, $msg) = record_ffq_prev_deferred();
     if ($status eq 'exists' && $opt_noop_ok) {
-	print "Previous head already recorded\n" or die $!;
+	print "Previous head already recorded\n" or confess $!;
     } elsif ($status eq 'deferred') {
 	run_deferred_updates 'record-ffq-prev';
     } else {
@@ -2174,13 +2256,13 @@ sub cmd_record_ffq_prev () {
 sub cmd_anchor () {
     badusage "no arguments allowed" if @ARGV;
     my ($anchor, $bw) = keycommits +(git_rev_parse 'HEAD'), 0,0;
-    print "$bw\n" or die $!;
+    print "$bw\n" or confess $!;
 }
 
 sub cmd_breakwater () {
     badusage "no arguments allowed" if @ARGV;
     my ($anchor, $bw) = keycommits +(git_rev_parse 'HEAD'), 0,0;
-    print "$bw\n" or die $!;
+    print "$bw\n" or confess $!;
 }
 
 sub cmd_status () {
@@ -2213,7 +2295,7 @@ sub cmd_status () {
 
     my $prcommitinfo = sub {
 	my ($cid) = @_;
-	flush STDOUT or die $!;
+	flush STDOUT or confess $!;
 	runcmd @git, qw(--no-pager log -n1),
 	    '--pretty=format:    %h %s%n',
 	    $cid;
@@ -2338,23 +2420,30 @@ sub make_patches_staged ($) {
     # laundered.
     my ($secret_head, $secret_bw, $last_anchor) = walk $head;
     fresh_workarea();
+    my $any;
     in_workarea sub {
-	gbp_pq_export 'bw', $secret_bw, $secret_head;
+	$any = gbp_pq_export 'bw', $secret_bw, $secret_head;
     };
+    return $any;
 }
 
 sub make_patches ($) {
     my ($head) = @_;
     keycommits $head, 0, \&snag;
-    make_patches_staged $head;
+    my $any = make_patches_staged $head;
     my $out;
     in_workarea sub {
-	my $ptree = cmdoutput @git, qw(write-tree --prefix=debian/patches/);
+	my $ptree = !$any ? undef :
+	    cmdoutput @git, qw(write-tree --prefix=debian/patches/);
 	runcmd @git, qw(read-tree), $head;
-	read_tree_subdir 'debian/patches', $ptree;
+	if ($ptree) {
+	    read_tree_subdir 'debian/patches', $ptree;
+	} else {
+	    rm_subdir_cached 'debian/patches';
+	}
 	$out = make_commit [$head], [
             'Commit patch queue (exported by git-debrebase)',
-            '[git-debrebase: export and commit patches]',
+            '[git-debrebase make-patches: export and commit patches]',
         ];
     };
     return $out;
@@ -2392,7 +2481,14 @@ sub check_series_has_all_patches ($) {
 	[qw(blob missing)];
     $series //= '';
     my %series;
+    our $comments_snagged;
     foreach my $f (grep /\S/, grep {!m/^\s\#/} split /\n/, $series) {
+	if ($f =~ m/^\s*\#/) {
+	    snag 'series-comments',
+		"$seriesfn contains comments, which will be discarded"
+		unless $comments_snagged++;
+	    next;
+	}
 	fail "patch $f repeated in $seriesfn !" if $series{$f}++;
     }
     foreach my $patchfile (get_tree "$head:debian/patches", 1,1) {
@@ -2403,13 +2499,36 @@ sub check_series_has_all_patches ($) {
     }
 }
 
+sub begin_convert_from () {
+    my $head = get_head();
+    my ($ffqs, $ffqm, $symref, $ffq_prev, $gdrlast) = ffq_prev_branchinfo();
+
+    fail "ffq-prev exists, this is already managed by git-debrebase!"
+	if $ffq_prev && git_get_ref $ffq_prev;
+
+    my $gdrlast_obj = $gdrlast && git_get_ref $gdrlast;
+    snag 'already-converted',
+	"ahead of debrebase-last, this is already managed by git-debrebase!"
+	if $gdrlast_obj && is_fast_fwd $gdrlast_obj, $head;
+    return ($head, { LastRef => $gdrlast, LastObj => $gdrlast_obj });
+}
+
+sub complete_convert_from ($$$$) {
+    my ($old_head, $new_head, $gi, $mrest) = @_;
+    ffq_check $new_head;
+    record_gdrlast $gi->{LastRef}, $new_head, $gi->{LastObj}
+	if $gi->{LastRef};
+    snags_maybe_bail();
+    update_head_checkout $old_head, $new_head, $mrest;
+}
+
 sub cmd_convert_from_gbp () {
     badusage "want only 1 optional argument, the upstream git commitish"
 	unless @ARGV<=1;
 
     my $clogp = parsechangelog();
     my $version = $clogp->{'Version'}
-	// die "missing Version from changelog";
+	// die "missing Version from changelog\n";
 
     my ($upstream_spec) = @ARGV;
 
@@ -2417,7 +2536,7 @@ sub cmd_convert_from_gbp () {
     my $upstream =
 	resolve_upstream_version($upstream_spec, $upstream_version);
 
-    my $old_head = get_head();
+    my ($old_head, $gdrlastinfo) = begin_convert_from();
 
     my $upsdiff = get_differs $upstream, $old_head;
     if ($upsdiff & D_UPS) {
@@ -2531,11 +2650,9 @@ END
 	}
     };
 
-    ffq_check $work;
-    snags_maybe_bail();
-    update_head_checkout $old_head, $work, 'convert-from-gbp';
-    print <<END or die $!;
-git-debrebase: converted from patched-unapplied (gbp) branch format, OK
+    complete_convert_from $old_head, $work, $gdrlastinfo, 'convert-from-gbp';
+    print <<END or confess $!;
+$us: converted from patched-unapplied (gbp) branch format, OK
 END
 }
 
@@ -2543,25 +2660,30 @@ sub cmd_convert_to_gbp () {
     badusage "no arguments allowed" if @ARGV;
     my $head = get_head();
     my (undef, undef, undef, $ffq, $gdrlast) = ffq_prev_branchinfo();
-    keycommits $head, 0;
-    my $out;
-    make_patches_staged $head;
-    in_workarea sub {
-	$out = make_commit ['HEAD'], [
-            'Commit patch queue (converted from git-debrebase format)',
-            '[git-debrebase convert-to-gbp: commit patches]',
-        ];
-    };
+    my ($anchor, $breakwater) = keycommits $head, 0;
+    my $out = $breakwater;
+    my $any = make_patches_staged $head;
+    if ($any) {
+	in_workarea sub {
+	    $out = make_commit [$out], [
+		'Commit patch queue (converted from git-debrebase format)',
+		'[git-debrebase convert-to-gbp: commit patches]',
+	    ];
+	};
+    } else {
+	# in this case, it can be fast forward
+	$out = $head;
+    }
     if (defined $ffq) {
 	push @deferred_updates, "delete $ffq";
 	push @deferred_updates, "delete $gdrlast";
     }
     snags_maybe_bail();
     update_head_checkout $head, $out, "convert to gbp (v0)";
-    print <<END or die $!;
-git-debrebase: converted to git-buildpackage branch format
-git-debrebase: WARNING: do not now run "git-debrebase" any more
-git-debrebase: WARNING: doing so would drop all upstream patches!
+    print <<END or confess $!;
+$us: converted to git-buildpackage branch format
+$us: WARNING: do not now run "git-debrebase" any more
+$us: WARNING: doing so would drop all upstream patches!
 END
 }
 
@@ -2593,7 +2715,7 @@ sub cmd_convert_from_dgit_view () {
 			 };
     }
 
-    my $head = get_head();
+    my ($head, $gdrlastinfo) = begin_convert_from();
 
     if (!$always) {
 	my $troubles = 0;
@@ -2638,7 +2760,7 @@ END
 	    # we do a quick check to see if there are plausible origs
 	    my $something=0;
 	    if (!opendir BPD, $bpd) {
-		die "$bpd: opendir: $!" unless $!==ENOENT;
+		die "opendir build-products-dir $bpd: $!" unless $!==ENOENT;
 	    } else {
 		while ($!=0, my $f = readdir BPD) {
 		    next unless is_orig_file_of_p_v $f, $p, $version;
@@ -2648,7 +2770,7 @@ END
 		    $something=1;
 		    last;
 		}
-		die "read $bpd: $!" if $!;
+		confess "read $bpd: $!" if $!;
 		closedir BPD;
 	    }
 	    if ($something) {
@@ -2665,7 +2787,7 @@ Import effective orig tree for upstream version $version
 END
 This includes the contents of the .orig(s), minus any debian/ directory.
 
-[git-debrebase import-from-dgit-view upstream-import-convert: $version]
+[git-debrebase convert-from-dgit-view upstream-import-convert: $version]
 END
 						    ];
 		    push @upstreams, { Commit => $ups_synth,
@@ -2699,7 +2821,7 @@ END
  'git-debrebase convert-from-dgit-view: drop upstream changes from breakwater',
  "Drop upstream changes, and delete debian/patches, as part of converting\n".
  "to git-debrebase format.  Upstream changes will appear as commits.",
- '[git-debrebase convert-from-dgit-view: drop patches from tree]'
+ '[git-debrebase convert-from-dgit-view drop-patches]'
 					   ];
 	    }
 	    $work = make_commit [ $work, $u->{Commit} ], [
@@ -2749,12 +2871,22 @@ END
 
     printf STDERR "Yes, will base new branch on %s\n", $result->{Source};
 
-    ffq_check $result->{Result};
-    snags_maybe_bail();
-    update_head_checkout $head, $result->{Result},
+    complete_convert_from $head, $result->{Result}, $gdrlastinfo,
 	'convert-from-dgit-view';
 }
 
+sub cmd_forget_was_ever_debrebase () {
+    badusage "forget-was-ever-debrebase takes no further arguments" if @ARGV;
+    my ($ffqstatus, $ffq_msg, $current, $ffq_prev, $gdrlast) =
+	ffq_prev_branchinfo();
+    fail "Not suitable for recording git-debrebaseness anyway: $ffq_msg"
+	if defined $ffq_msg;
+    push @deferred_updates, "delete $ffq_prev";
+    push @deferred_updates, "delete $gdrlast";
+    snags_maybe_bail();
+    run_deferred_updates "forget-was-ever-debrebase";
+}
+
 sub cmd_record_resolved_merge () {
     badusage "record-resolved-merge takes no further arguments" if @ARGV;
     # MERGE-TODO needs documentation
@@ -2844,6 +2976,9 @@ sub cmd_downstream_rebase_launder_v0 () {
     }
 }
 
+setlocale(LC_MESSAGES, "");
+textdomain("git-debrebase");
+
 getoptions_main
           ("bad options\n",
 	   "D+" => \$debuglevel,
@@ -2852,11 +2987,12 @@ getoptions_main
 	   'anchor=s' => \@opt_anchors,
 	   '--dgit=s' => \($dgit[0]),
 	   'force!',
+	   'experimental-merge-resolution!', \$opt_merges,
 	   '-i:s' => sub {
 	       my ($opt,$val) = @_;
-	       badusage "git-debrebase: no cuddling to -i for git-rebase"
+	       badusage f_ "%s: no cuddling to -i for git-rebase", $us
 		   if length $val;
-	       die if $opt_defaultcmd_interactive; # should not happen
+	       confess if $opt_defaultcmd_interactive; # should not happen
 	       $opt_defaultcmd_interactive = [ qw(-i) ];
 	       # This access to @ARGV is excessive familiarity with
 	       # Getopt::Long, but there isn't another sensible
@@ -2864,14 +3000,14 @@ getoptions_main
 	       push @$opt_defaultcmd_interactive, @ARGV;
 	       @ARGV=();
 	   },
-	   'help' => sub { print $usage_message or die $!; finish 0; },
+	   'help' => sub { print __ $usage_message or confess $!; finish 0; },
 	   );
 
 initdebug('git-debrebase ');
 enabledebug if $debuglevel;
 
 my $toplevel = cmdoutput @git, qw(rev-parse --show-toplevel);
-chdir $toplevel or die "chdir $toplevel: $!";
+chdir $toplevel or fail "chdir toplevel $toplevel: $!\n";
 
 $rd = fresh_playground "$playprefix/misc";
 
@@ -2885,7 +3021,7 @@ if (!@ARGV || $opt_defaultcmd_interactive || $ARGV[0] =~ m{^-}) {
     $cmdfn =~ y/-/_/;
     $cmdfn = ${*::}{"cmd_$cmdfn"};
 
-    $cmdfn or badusage "unknown git-debrebase sub-operation $cmd";
+    $cmdfn or badusage f_ "unknown git-debrebase sub-operation %s", $cmd;
     $cmdfn->();
 }