mmit message, start the editor with the
contents in the given file.  The <code>commit.template</code> configuration
variable is often used to give this option implicitly to the
command.  This mechanism can be used by projects that want to
guide participants with some hints on what to write in the message
in what order.  If the user exits the editor without editing the
message, the commit is aborted.  This has no effect when a message
is given by other means, e.g. with the <code>-m</code> or <code>-F</code> 