doc: typeset long command-line options as literal

Similarly to the previous commit, use backquotes instead of
forward-quotes, for long options.

This was obtained with:

  perl -pi -e "s/'(--[a-z][a-z=<>-]*)'/\`\$1\`/g" *.txt

and manual tweak to remove false positive in ascii-art (o'--o'--o' to
describe rewritten history).

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/gitcore-tutorial.txt b/Documentation/gitcore-tutorial.txt
index 15b3bfa..4546fa0 100644
--- a/Documentation/gitcore-tutorial.txt
+++ b/Documentation/gitcore-tutorial.txt
@@ -949,7 +949,7 @@
 [NOTE]
 If there were more commits on the 'master' branch after the merge, the
 merge commit itself would not be shown by 'git show-branch' by
-default.  You would need to provide '--sparse' option to make the
+default.  You would need to provide `--sparse` option to make the
 merge commit visible in this case.
 
 Now, let's pretend you are the one who did all the work in