[git-clang-format] Add some examples to the help text

Differential Revision: https://reviews.llvm.org/D124282

NOKEYCHECK=True
GitOrigin-RevId: a45764f2f9cf0d2d6ec5bd871cc9c36ebf785ccc
diff --git a/git-clang-format b/git-clang-format
index 1d6f216..86f4497 100755
--- a/git-clang-format
+++ b/git-clang-format
@@ -40,6 +40,16 @@
 between the working directory and <commit>, which defaults to HEAD.  Changes are
 only applied to the working directory, or in the stage/index.
 
+Examples:
+  To format staged changes, i.e everything that's been `git add`ed:
+    git clang-format
+
+  To also format everything touched in the most recent commit:
+    git clang-format HEAD~1
+
+  If you're on a branch off main, to format everything touched on your branch:
+    git clang-format main
+
 If two commits are given (requires --diff), run clang-format on all lines in the
 second <commit> that differ from the first <commit>.