git-debrebase: document that breakwater merges always have single parent

[dgit.git] / git-debrebase

diff --git a/git-debrebase b/git-debrebase
index e73526e9e6207606df78647aa5b902e9580175da..5808cf33f7f1b702f29c5e57b1ef01e707a0428f 100755 (executable)
--- a/git-debrebase
+++ b/git-debrebase
@@ -104,14 +104,15 @@
 
 use strict;
 
+use Debian::Dgit qw(:DEFAULT :playground);
+setup_sigwarn();
+
 use Memoize;
 use Carp;
 use POSIX;
 use Data::Dumper;
 use Getopt::Long qw(:config posix_default gnu_compat bundling);
 
-use Debian::Dgit qw(:DEFAULT :playground);
-
 sub badusage ($) {
     my ($m) = @_;
     die "bad usage: $m\n";
@@ -153,7 +154,8 @@ sub in_workarea ($) {
     my ($sub) = @_;
     changedir $workarea;
     my $r = eval { $sub->(); };
-    changedir $maindir;
+    { local $@; changedir $maindir; }
+    die $@ if $@;
 }
 
 sub fresh_workarea () {
@@ -211,7 +213,7 @@ sub get_differs ($$) {
            }
            die unless s{^debian/patches/}{};
            my $ok;
-           if ($mode eq 'A' && !m/(?:^|\.)series$/s) {
+           if ($mode eq 'A' && !m/\.series$/s) {
                $ok = 1;
            } elsif ($mode eq 'M' && $_ eq 'series') {
                my $x_s = git_cat_file "$x:debian/patches/series", 'blob';
@@ -281,7 +283,7 @@ sub calculate_committer_authline () {
 #
 #   BreakwaterUpstreamMerge
 #     has additional entry in classification result
-#       OrigParents = [ subset of Parents ]
+#       OrigParents = [ subset of Parents ]  # singleton list
 
 sub classify ($) {
     my ($objid) = @_;
@@ -304,7 +306,7 @@ sub classify ($) {
        push @p, {
             Ix => $#p,
             CommitId => $ph,
-            Differs => (get_differs $t, $ph),
+            Differs => (get_differs $ph, $t),
         };
     }
 
@@ -474,7 +476,9 @@ sub walk ($;$$) {
        if ($nogenerate) {
            return (undef,undef);
        }
-       die "commit $cur: Cannot cope with this commit";
+       die "commit $cur: Cannot cope with this commit (d.".
+           (join ' ', map { sprintf "%#x", $_->{Differs} }
+            @{ $cl->{Parents} }). ")";
     };
 
     my $build;
@@ -512,7 +516,7 @@ sub walk ($;$$) {
        } elsif ($ty eq 'Mixed') {
            my $queue = sub {
                my ($q, $wh) = @_;
-               my $cls = { $cl, $xmsg->("split mixed commit: $wh part") };
+               my $cls = { %$cl, $xmsg->("split mixed commit: $wh part") };
                push @$q, $cls;
            };
            $queue->(\@brw_cl, "debian");
@@ -624,9 +628,14 @@ sub walk ($;$$) {
  
     my $committer_authline = calculate_committer_authline();
 
+    printdebug "WALK REBUILD $build ".(scalar @processed)."\n";
+
+    confess "internal error" unless $build eq (pop @processed)->{CommitId};
+
     in_workarea sub {
        mkdir $rd or $!==EEXIST or die $!;
        my $current_method;
+       runcmd @git, qw(read-tree), $build;
        foreach my $cl (qw(Debian), (reverse @brw_cl),
                        { SpecialMethod => 'RecordBreakwaterTip' },
                        qw(Upstream), (reverse @upp_cl)) {
@@ -637,6 +646,8 @@ sub walk ($;$$) {
            my $method = $cl->{SpecialMethod} // $current_method;
            my @parents = ($build);
            my $cltree = $cl->{CommitId};
+           printdebug "WALK BUILD ".($cltree//'undef').
+               " $method (rewriting=$rewriting)\n";
            if ($method eq 'Debian') {
                $read_tree_debian->($cltree);
            } elsif ($method eq 'Upstream') {
@@ -656,13 +667,19 @@ sub walk ($;$$) {
            } else {
                confess "$method ?";
            }
-           $rewriting ||= $cl ne pop @processed;
+           if (!$rewriting) {
+               my $procd = (pop @processed) // 'UNDEF';
+               if ($cl ne $procd) {
+                   $rewriting = 1;
+                   printdebug "WALK REWRITING NOW cl=$cl procd=$procd\n";
+               }
+           }
            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
+               join '', map { "parent $_\n" } @parents
            }me or confess "$ch ?";
            if ($rewriting) {
                $ch =~ s{^committer .*$}{$committer_authline}m
@@ -681,7 +698,9 @@ sub walk ($;$$) {
        }
     };
 
-    runcmd @git, qw(diff-tree --quiet), $input, $build;
+    my $final_check = get_differs $build, $input;
+    die sprintf "internal error %#x %s %s", $final_check, $build, $input
+       if $final_check & ~D_PAT_ADD;
 
     return ($build, $breakwater);
 }
@@ -706,8 +725,9 @@ sub cmd_launder () {
     my ($tip,$breakwater) = walk $old;
     update_head $old, $tip, 'launder';
     # no tree changes except debian/patches
-    runcmd @git, qw(rm --quiet -rf debian/patches);
+    runcmd @git, qw(rm --quiet --ignore-unmatch -rf debian/patches);
     printf "# breakwater tip\n%s\n", $breakwater;
+    printf "# working tip\n%s\n", $tip;
 }
 
 sub cmd_analyse () {
@@ -724,7 +744,7 @@ sub cmd_analyse () {
 }
 
 sub cmd_downstream_rebase_launder_v0 () {
-    badusage "needs 1 argument, the baseline" unless @ARGV=0;
+    badusage "needs 1 argument, the baseline" unless @ARGV==1;
     my ($base) = @ARGV;
     $base = git_rev_parse $base;
     my $old_head = get_head();
@@ -732,24 +752,25 @@ sub cmd_downstream_rebase_launder_v0 () {
     my $topmost_keep;
     for (;;) {
        if ($current eq $base) {
-           $topmust_keep //= $current;
-           print "$current BASE: stopping\n";
+           $topmost_keep //= $current;
+           print " $current BASE stop\n";
            last;
        }
        my $cl = classify $current;
        print " $current $cl->{Type}";
        my $keep = 0;
        my $p0 = $cl->{Parents}[0]{CommitId};
+       my $next;
        if ($cl->{Type} eq 'Pseudomerge') {
-           $current = $cl->{Contributor}{CommitId};
            print " ^".($cl->{Contributor}{Ix}+1);
+           $next = $cl->{Contributor}{CommitId};
        } elsif ($cl->{Type} eq 'AddPatches' or
                 $cl->{Type} eq 'Changelog') {
            print " strip";
-           $current = $p0;
+           $next = $p0;
        } else {
            print " keep";
-           $current = $p0;
+           $next = $p0;
            $keep = 1;
        }
        print "\n";
@@ -757,14 +778,17 @@ sub cmd_downstream_rebase_launder_v0 () {
            $topmost_keep //= $current;
        } else {
            die "to-be stripped changes not on top of the branch\n"
-               if $topmost_unstripped;
+               if $topmost_keep;
        }
+       $current = $next;
     }
     if ($topmost_keep eq $old_head) {
        print "unchanged\n";
     } else {
        print "updating to $topmost_keep\n";
-       update_head $old_head, $topmost_keep, 'downstream-rebase-launder-v0';
+       update_head_checkout
+           $old_head, $topmost_keep,
+           'downstream-rebase-launder-v0';
     }
 }