The "amend" command:
Usage: fossil amend HASH OPTION ?OPTION ...?
Amend the tags on check-in HASH to change how it displays in the timeline.
Options:
- --author USER
 - Make USER the author for check-in
 - -m|--comment COMMENT
 - Make COMMENT the check-in comment
 - -M|--message-file FILE
 - Read the amended comment from FILE
 - -e|--edit-comment
 - Launch editor to revise comment
 - --date DATETIME
 - Make DATETIME the check-in time
 - --bgcolor COLOR
 - Apply COLOR to this check-in
 - --branchcolor COLOR
 - Apply and propagate COLOR to the branch
 - --tag TAG
 - Add new TAG to this check-in
 - --cancel TAG
 - Cancel TAG from this check-in
 - --branch NAME
 - Make this check-in the start of branch NAME
 - --hide
 - Hide branch starting from this check-in
 - --close
 - Mark this "leaf" as closed
 - -n|--dry-run
 - Print control artifact, but make no changes
 - --date-override DATETIME
 - Set the change time on the control artifact
 - --user-override USER
 - Set the user name on the control artifact
 
DATETIME may be "now" or "YYYY-MM-DDTHH:MM:SS.SSS". If in year-month-day form, it may be truncated, the "T" may be replaced by a space, and it may also name a timezone offset from UTC as "-HH:MM" (westward) or "+HH:MM" (eastward). Either no timezone suffix or "Z" means UTC.