The "git" command:

Usage: fossil git SUBCOMMAND

Do incremental import or export operations between Fossil and Git.
Subcommands:

  fossil git export [MIRROR] [OPTIONS]

      Write content from the Fossil repository into the Git repository
      in directory MIRROR.  The Git repository is created if it does not
      already exist.  If the Git repository does already exist, then
      new content added to fossil since the previous export is appended.

      Repeat this command whenever new checkins are added to the Fossil
      repository in order to reflect those changes into the mirror.  If
      the MIRROR option is omitted, the repository from the previous
      invocation is used.

      The MIRROR directory will contain a subdirectory named
      ".mirror_state" that contains information that Fossil needs to
      do incremental exports.  Do not attempt to manage or edit the files
      in that directory since doing so can disrupt future incremental
      exports.

      Options:
        --autopush URL      Automatically do a 'git push' to URL.  The
                            URL is remembered and used on subsequent exports
                            to the same repository.  Or if URL is "off" the
                            auto-push mechanism is disabled
        --debug FILE        Write fast-export text to FILE rather than
                            piping it into "git fast-import".
        --force|-f          Do the export even if nothing has changed
        --limit N           Add no more than N new check-ins to MIRROR.
                            Useful for debugging
        --quiet|-q          Reduce output. Repeat for even less output.
        --verbose|-v        More output.

  fossil git import MIRROR

      TBD...   

  fossil git status

      Show the status of the current Git mirror, if there is one.