[PATCH] fix tutorial typo

Fix a minor typo in the tutorial.txt.

Signed-off-by: Jon Loeliger <jdl@freescale.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/tutorial.txt

@@ -742,7 +742,7 @@ git commit -m 'Some work.' hello
 ------------------------------------------------
 
 Here, we just added another line to `hello`, and we used a shorthand for
-both going a `git-update-index hello` and `git commit` by just giving the
+doing both `git-update-index hello` and `git commit` by just giving the
 filename directly to `git commit`. The `-m` flag is to give the
 commit log message from the command line.