Showing Which Sections Differences Are in
Sometimes you might want to know which part of the files each change
falls in. If the files are source code, this could mean which function
was changed. If the files are documents, it could mean which chapter or
appendix was changed. GNU
diff can show this by displaying the
nearest section heading line that precedes the differing lines. Which
lines are "section headings" is determined by a regular expression.