Ignore *all* whitespace changes with git-diff between commits

Question

I'm going through a codebase and fixing whitespace oddities and generally correcting indentation and such things, and I want to make sure I haven't inadvertently made any other changes, so I'm doing git diff -w to display differences in all changed files while ignoring whitespace differences. The problem is that this is not actually ignoring all whitespace differences—at least what I consider to be merely whitespace differences. For instance, in the following output from git diff -w,

-"Links":
-{
-
-    "Thermal":
-
-{
-
+  "Links": {
+    "Thermal": {

you can see that I've only

1. removed superfluous blank lines,
2. put curly braces on the end of the line of the key whose value they open, and
3. indented to fit the context

This question looked like it might offer an answer at first, but it deals with differences between two specific files, not between two specific commits. Everything else turned up by searching was a dead end as well. For instance, this question is about merging, not displaying differences, and this question deals with displaying word-level differences, and so forth.

Answer 1

Perhaps there is a better answer, but the best solution I've found so far is this.

First, you must control the definition of "whitespace" that Git is currently using.

git config core.whitespace '-trailing-space,-indent-with-non-tab,-tab-in-indent'

Next, you must control the definition of a word used. Instead of just using git diff -w, add --word-diff-regex='[^[:space:]]':

git diff -w --word-diff-regex='[^[:space:]]'

You'll still see the context, which (in my case, since I'm trying to ensure that there are no differences except whitespace differences) is not helpful. You can use -U0 to tell Git to give you 0 lines of context, like so,

git diff -w -U0 --word-diff-regex='[^[:space:]]'

but you'll still get output that looks pretty much like context, but it's still much better than looking through all the changes carefully and manually to make sure they are only whitespace changes.

You can also do all the above in one command. The -c flag changes git config just for one command.

git -c core.whitespace=-trailing-space,-indent-with-non-tab,-tab-in-indent diff -U0 --word-diff-regex='[^[:space:]]'