The "co" command:

Usage: fossil checkout ?VERSION | --latest? ?OPTIONS?
   or: fossil co ?VERSION | --latest? ?OPTIONS?

Check out a version specified on the command-line.  This command
will abort if there are edited files in the current checkout unless
the --force option appears on the command-line.  The --keep option
leaves files on disk unchanged, except the manifest and manifest.uuid
files.

The --latest flag can be used in place of VERSION to checkout the
latest version in the repository.

Options:
   --force           Ignore edited files in the current checkout
   --keep            Only update the manifest and manifest.uuid files
   --force-missing   Force checkout even if content is missing
   --setmtime        Set timestamps of all files to match their SCM-side
                     times (the timestamp of the last checkin which modified
                     them).

See also: update