The "open" command:

Usage: fossil open FILENAME ?VERSION? ?OPTIONS?

Open a connection to the local repository in FILENAME.  A checkout
for the repository is created with its root at the working directory.
If VERSION is specified then that version is checked out.  Otherwise
the latest version is checked out.  No files other than "manifest"
and "manifest.uuid" are modified if the --keep option is present.

Options:
  --empty           Initialize checkout as being empty, but still connected
                    with the local repository. If you commit this checkout,
                    it will become a new "initial" commit in the repository.
  --keep            Only modify the manifest and manifest.uuid files
  --nested          Allow opening a repository inside an opened checkout
  --force-missing   Force opening a repository with missing content
  --setmtime        Set timestamps of all files to match their SCM-side
                    times (the timestamp of the last checkin which modified
                    them).

See also: close