The "login-group" command:
Usage: fossil login-group
or: fossil login-group join REPO [-name NAME]
or: fossil login-group leave
With no arguments, this command shows the login-group to which the
repository belongs.
The "join" command adds this repository to login group to which REPO
belongs, or creates a new login group between itself and REPO if REPO
does not already belong to a login-group. When creating a new login-
group, the name of the new group is determined by the "--name" option.
The "leave" command takes the repository out of whatever login group
it is currently a part of.
About Login Groups:
A login-group is a set of repositories that share user credentials.
If a user is logged into one member of the group, then that user can
access any other group member as long as they have an entry in the
USER table of that member. If a user changes their password using
web interface, their password is also automatically changed in every
other member of the login group.