The "rename" command:

Usage: fossil mv|rename OLDNAME NEWNAME
   or: fossil mv|rename OLDNAME... DIR

Move or rename one or more files or directories within the repository tree.
You can either rename a file or directory or move it to another subdirectory.

This command does NOT rename or move the files on disk.  This command merely
records the fact that filenames have changed so that appropriate notations
can be made at the next commit/checkin.

See also: changes, status