examples/commit: use --abbrev for commit summary

After v1.7.1.1~17^2~3 (pretty: Respect --abbrev option, 2010-05-03),
plumbing users do not abbreviate %h hashes by default any more.

Noticed while investigating the bug fixed by v1.7.1.1~17^2
(commit::print_summary(): don't use format_commit_message(),
2010-06-12).

Cc: Will Palmer <wmpalmer@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jrn

contrib/examples/git-commit.sh

@@ -631,7 +631,7 @@ then
 	if test -z "$quiet"
 	then
 		commit=`git diff-tree --always --shortstat --pretty="format:%h: %s"\
-		       --summary --root HEAD --`
+		       --abbrev --summary --root HEAD --`
 		echo "Created${initial_commit:+ initial} commit $commit"
 	fi
 fi