Add Highlight Extra Whitespace In Diff Output as a Git TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1534 TILs and counting..._
+_1535 TILs and counting..._
 
 ---
 
@@ -317,6 +317,7 @@ _1534 TILs and counting..._
 - [Grab A Single File From A Stash](git/grab-a-single-file-from-a-stash.md)
 - [Grep For A Pattern On Another Branch](git/grep-for-a-pattern-on-another-branch.md)
 - [Grep Over Commit Messages](git/grep-over-commit-messages.md)
+- [Highlight Extra Whitespace In Diff Output](git/highlight-extra-whitespace-in-diff-output.md)
 - [Ignore Changes To A Tracked File](git/ignore-changes-to-a-tracked-file.md)
 - [Ignore Files Specific To Your Workflow](git/ignore-files-specific-to-your-workflow.md)
 - [Include A Message With Your Stashed Changes](git/include-a-message-with-your-stashed-changes.md)

git/highlight-extra-whitespace-in-diff-output.md

@@ -0,0 +1,30 @@
+# Highlight Extra Whitespace In Diff Output
+
+When running a `git diff` (or `git add --patch`) I'll sometimes come across
+lines that don't have any visible changes. This is usually because some
+whitespace characters were either added (on accident) or removed (often by a
+autoformatter).
+
+Depending on the `core.whitespace` config, you'll probably see at least some of
+the whitespace errors that git provides. By default, git only highlights
+whitespace errors on added (`new`) lines. However if some extra whitespace was
+originally committed and is now being removed, it won't be highlighted on the
+`old` line in the diff.
+
+We can have git always highlight whitespace errors by setting
+`wsErrorHighlight` to `all` in the global git config.
+
+```bash
+$ git config --global diff.wsErrorHighlight all
+```
+
+Which updates the global gitconfig file with the following line:
+
+```
+[diff]
+	wsErrorHighlight = all
+```
+
+The `all` option is a shorthand for `old,new,context`.
+
+See `man git-diff` for more details.