t1408: add a test of stale packed refs covered by loose refs

It is OK for the packed-refs file to contain old reference definitions
that might even refer to objects that have since been
garbage-collected, as long as there is a corresponding loose reference
definition that overrides it. Add a test that such references don't
cause problems.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1408-packed-refs.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+
+test_description='packed-refs entries are covered by loose refs'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_tick &&
+	git commit --allow-empty -m one &&
+	one=$(git rev-parse HEAD) &&
+	git for-each-ref >actual &&
+	echo "$one commit	refs/heads/master" >expect &&
+	test_cmp expect actual &&
+
+	git pack-refs --all &&
+	git for-each-ref >actual &&
+	echo "$one commit	refs/heads/master" >expect &&
+	test_cmp expect actual &&
+
+	git checkout --orphan another &&
+	test_tick &&
+	git commit --allow-empty -m two &&
+	two=$(git rev-parse HEAD) &&
+	git checkout -B master &&
+	git branch -D another &&
+
+	git for-each-ref >actual &&
+	echo "$two commit	refs/heads/master" >expect &&
+	test_cmp expect actual &&
+
+	git reflog expire --expire=now --all &&
+	git prune &&
+	git tag -m v1.0 v1.0 master
+'
+
+test_expect_success 'no error from stale entry in packed-refs' '
+	git describe master >actual 2>&1 &&
+	echo "v1.0" >expect &&
+	test_cmp expect actual
+'
+
+test_done