shortlog: do not require to run from inside a git repository

Once upon a time shortlog could be run from a non-git directory
and still do its job. Fix this regression and add a small test
for it.

Signed-off-by: Jonas Fonseca <fonseca@diku.dk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-shortlog.c

@@ -229,7 +229,9 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 {
 	struct shortlog log;
 	struct rev_info rev;
+	int nongit;
 
+	prefix = setup_git_directory_gently(&nongit);
 	shortlog_init(&log);
 
 	/* since -n is a shadowed rev argument, parse our args first */
@@ -259,7 +261,7 @@ int cmd_shortlog(int argc, const char **argv, const char *prefix)
 		die ("unrecognized argument: %s", argv[1]);
 
 	/* assume HEAD if from a tty */
-	if (!rev.pending.nr && isatty(0))
+	if (!nongit && !rev.pending.nr && isatty(0))
 		add_head_to_pending(&rev);
 	if (rev.pending.nr == 0) {
 		read_from_stdin(&log);

git.c

@@ -343,7 +343,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "revert", cmd_revert, RUN_SETUP | NEED_WORK_TREE },
 		{ "rm", cmd_rm, RUN_SETUP },
 		{ "send-pack", cmd_send_pack, RUN_SETUP },
-		{ "shortlog", cmd_shortlog, RUN_SETUP | USE_PAGER },
+		{ "shortlog", cmd_shortlog, USE_PAGER },
 		{ "show-branch", cmd_show_branch, RUN_SETUP },
 		{ "show", cmd_show, RUN_SETUP | USE_PAGER },
 		{ "status", cmd_status, RUN_SETUP | NEED_WORK_TREE },

t/t4201-shortlog.sh

@@ -47,4 +47,9 @@ EOF
 
 test_expect_success 'shortlog wrapping' 'diff -u expect out'
 
+git log HEAD > log
+GIT_DIR=non-existing git shortlog -w < log > out
+
+test_expect_success 'shortlog from non-git directory' 'diff -u expect out'
+
 test_done