+ read_tree_subdir 'debian', "$breakwater:debian";
+
+ # index now contains the breakwater merge contents
+
+ my $bw_tree = cmdoutput @git, qw(write_tree);
+ my @cmd = (@git, qw(commit-tree), $bw_tree);
+ push @cmd, qw(-p), $breakwater, qw(-p), $new_upstream;
+ push @cmd, qw(-m), "Update to upstream $new_upstream_version";
+ push @cmd, qw(-m),
+ "[git-debrebase new-upstream breakwater $new_upstream_version]";
+ my $new_bw = cmdoutput @git;
+
+ # Now we have to add a changelog stanza so the Debian version
+ # is right.
+
+ die if unlink "debian";
+ die unless $!==ENOTEMPTY;
+ unlink "debian/changelog" 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.
+
+ --
+
+END
+ close CN or die $!;
+ runcmd @git, qw(update-index --add --replace), 'debian/changelog';
+
+ # Now we have the final new breakwater branch in the index
+
+ $bw_tree = cmdoutput @git, qw(write_tree);
+ @cmd = (@git, qw(commit-tree), $bw_tree);
+ push @cmd, qw(-p), $new_bw;
+ push @cmd, qw(-m),
+ "Update changelog for new upstream $new_upstream_version";
+ push @cmd, qw(-m),
+ "[git-debrebase new-upstream changelog $new_upstream_version]";
+ $new_bw = cmdoutput @git;
+