shortlog: use pager

On request of the kingpenguin, shortlog now uses the pager if output
goes to a tty.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git.c

@@ -260,7 +260,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "rev-parse", cmd_rev_parse, RUN_SETUP },
 		{ "rm", cmd_rm, RUN_SETUP },
 		{ "runstatus", cmd_runstatus, RUN_SETUP },
-		{ "shortlog", cmd_shortlog, RUN_SETUP },
+		{ "shortlog", cmd_shortlog, RUN_SETUP | USE_PAGER },
 		{ "show-branch", cmd_show_branch, RUN_SETUP },
 		{ "show", cmd_show, RUN_SETUP | USE_PAGER },
 		{ "stripspace", cmd_stripspace },