The "login-group" command:

Run various subcommands to manage login-group related settings of the open repository or of the repository identified by the -R or --repository option.

fossil login-group ?-R REPO?

Show the login-group to which REPO, or if invoked from within a check-out the repository on which the current check-out is based, belongs.

fossil login-group join ?-R REPO? ?--name NAME? REPO2

This command will either: (1) add the repository on which the current check-out is based, or the repository REPO specified with -R, to the login group where REPO2 is a member, in which case the optional --name argument is not required; or (2) create a new login group between the repository on which the current check-out is based, or the repository REPO specified with -R, and REPO2, in which case the new group NAME is determined by the mandatory --name option. In both cases, the specified repositories will first leave any group in which they are currently a member before joining the new login group.

fossil login-group leave ?-R REPO?

Take the repository REPO, or if invoked from within a check-out the repository on which the current check-out is based, out of whatever login group it is a member.

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.