Conceptually, this isn't much different from a summary. say we decide that 8-50 chars is a reasonable default summary length, and add text to shorter summaries. Some simple possible cases:
1) minor edit. one word changed, no summary. summary changed to read "'// word1 --> word2" 2) minor edit. a few words changed, summary 'typos'. summary changed to read "typos // word1 --> word2, word3 --> word4, ..." 3) major edit. a few sentences moved around. summary "rewrite". summary changed to read "rewrite // 'Start of first old changed para...' --> 'New paragraph...' "
Or rather than changing summaries, which might actually be metadata useful for something in the future, we should make the places where we see lists of changes (history, RC, etc) show some of the change text itself.
We could also add ways to see a larger chunk of changed text; this is just a simple suggestion for enhancing the current interface (and the metadata in the database)