Documentation: git-init: flesh out example

Add a third step `git commit` after adding files for the first time.

Signed-off-by: Linus Arver <linusarver@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-init.txt

@@ -141,10 +141,12 @@ Start a new Git repository for an existing code base::
 $ cd /path/to/my/codebase
 $ git init      <1>
 $ git add .     <2>
+$ git commit    <3>
 ----------------
 +
 <1> Create a /path/to/my/codebase/.git directory.
 <2> Add all existing files to the index.
+<3> Record the pristine state as the first commit in the history.
 
 GIT
 ---