doc/clone: Pick more compelling paths for the --reference example

There may be times when using one of your local repositories as a
reference for a new clone make sense, but the implied version-bump in
the old example isn't one of them.  I think a more intuitive example
is multi-user system with a central reference clone, and the new paths
hint at this use case.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-clone.txt

@@ -257,10 +257,10 @@ $ git show-branch
 * Clone from upstream while borrowing from an existing local directory:
 +
 ------------
-$ git clone --reference my2.6 \
-	git://git.kernel.org/pub/scm/.../linux-2.7 \
-	my2.7
-$ cd my2.7
+$ git clone --reference /git/linux.git \
+	git://git.kernel.org/pub/scm/.../linux.git \
+	my-linux
+$ cd my-linux
 ------------