Add a missed step.

Gerry · Gerry · commit 2e8dda469832 · 2017-06-09T17:21:56.000+08:00
diff --git a/book/10-git-internals/sections/objects.asc b/book/10-git-internals/sections/objects.asc
@@ -188,6 +188,8 @@ tree
 [source,console]
 ----
 $ echo 'new file' > new.txt
+$ git update-index --cacheinfo 100644 \
+  1f7a7a472abf3dd9643fd615f6da379c4acb3e3a test.txt
 $ git update-index test.txt
 $ git update-index --add new.txt
 ----
