initdebug('git-debrebase ');
enabledebug if $debuglevel;
-my $toplevel = cmdoutput @git, qw(rev-parse --show-toplevel);
-chdir $toplevel or fail f_ "chdir toplevel %s: %s\n", $toplevel, $!;
+changedir_git_toplevel();
$rd = fresh_playground "$playprefix/misc";