diff --git a/README.md b/README.md
index e06d555..88f5c8f 100644
--- a/README.md
+++ b/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).
 
-_1423 TILs and counting..._
+_1424 TILs and counting..._
 
 ---
 
@@ -261,6 +261,7 @@ _1423 TILs and counting..._
 
 - [Accessing a Lost Commit](git/accessing-a-lost-commit.md)
 - [Add A Range Of Filename To gitignore](git/add-a-range-of-filenames-to-gitignore.md)
+- [Add Only Tracked Files From A Directory](git/add-only-tracked-files-from-a-directory.md)
 - [Amend Author Of Previous Commit](git/amend-author-of-previous-commit.md)
 - [Auto-Squash Those Fixup Commits](git/auto-squash-those-fixup-commits.md)
 - [Caching Credentials](git/caching-credentials.md)
diff --git a/git/add-only-tracked-files-from-a-directory.md b/git/add-only-tracked-files-from-a-directory.md
new file mode 100644
index 0000000..6b79438
--- /dev/null
+++ b/git/add-only-tracked-files-from-a-directory.md
@@ -0,0 +1,26 @@
+# Add Only Tracked Files From A Directory
+
+The two extremes of staging files in a git repo are to either selectively pick
+each individual chunk of changes with `git add --patch` (my preference!) or to
+run `git add -A` to add everything.
+
+Now let's say I have large directory full of files that get generated during
+test runs. Most of these files are tracked (already checked in to the
+repository). There are also many new files generated as part of the most recent
+test run.
+
+I want to staging the changes to files that are already tracked, but hold off
+on doing anything with the new files.
+
+Running `git add spec/cassettes` won't do the track because that will pull in
+everything. Running `git add --patch spec/cassettes` will take long and be
+tedious. Instead what I want is the `-u` flag. It's short for _update_ which
+means it will only stage already tracked files.
+
+```bash
+$ git add -u spec/cassettes
+```
+
+That will stage every change to any already known files in `spec/cassettes`.
+
+See `man git-add` for more details.