Sometimes, the editing only changes one or two lines,
which means that the change may be self-describing .
It may be trivial to add a summary to this kind of editing,
(the summary is usually as same as the diff of that editing.)
but if the summary is omitted, the revision history page
will give no information about the revision.
Is it possible to generate summary from diff if summary is not given?
or other suggest or best practice?