Say I get a patch created with git format-patch. The file is basically a unified diff with some metadata. If I open the file in Vim, I can see which lines have been modified, but I cannot see which characters in the changed lines differ. Does anyone know a way (in Vim, or some other free software that runs on Ubuntu) to visualize per-character differences?
A counter example where per-character diff is visualized is when executing vimdiff a b.
update Fri Nov 12 22:36:23 UTC 2010
diffpatch is helpful for the scenario where you're working with a single file.
update Thu Jun 16 17:56:10 UTC 2016
Check out diff-highlight in git 2.9. This script does exactly what I was originally seeking.
Given your references to Vim in the question, I'm not sure if this is the answer you want :) but Emacs can do this. Open the file containing the diff, make sure that you're in diff-mode (if the file is named foo.diff or foo.patch this happens automatically; otherwise type M-x diff-mode RET), go to the hunk you are interested in and hit C-c C-b for refine-hunk. Or step through the file one hunk at a time with M-n; that will do the refining automatically.