change group password in batch mode

[Jonas Meurer <ansti@phreaker.net>]

hello,

for lurker i need to set the lurker system group password in postinst.
unfortunately there seems to be no way for changing group passwords in
batch mode.

for system user passwords 'chpasswd' exists, but i cannot find an
equivalent for system group passwords.

would it be generally useful? if yes, i could try to create a patch for
the shadow package to ship a 'chgpasswd' binary.

...
 jonas