How do I create a manual diff?

I have an existing codebase that I'd like to开发者_JS百科 highlight particular portions of for demonstration purposes. We use Review Board, which allows a user to upload a diff and conveniently compare it against the repository in question.

That given, is there a good way to create a diff manually so it will show the relevant portions as having been added? The only way that comes to mind is by deleting the relevant code and reversing the diff.

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Use diff command manually:

cp yourfile.py yourfile.py.orig
# then edit the file
# and generate the diff
diff -Naur yourfile.py.orig yourfile.py

If you are already using a version control software (like git, svn, hg...), you can directly use them before commit:

hg diff
git diff
svn diff