vcs_info doesn't work due to the '-'/Dash problem.
It fails at line 6 of VCS_INFO_get_cmd:
vcs_comm[cmd]=${cmd:-$vcs}
In gettokstr(), seen_brct is set to 1 by the '[' and
never reset to 0, and the '-' is converted to Dash.
% x=
% y=yes
% echo ${x:-$y}
yes
% a[1]=${x:-$y}
% echo '<'$a[1]'>'
<>