From 12a258c078da3481a5735a7dca00bbe75cd4713b Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Thu, 28 Jan 2010 04:56:43 -0500
Subject: reject @{-1} not at beginning of object name

Something like foo@{-1} is nonsensical, as the @{-N} syntax
is reserved for "the Nth last branch", and is not an actual
reflog selector. We should not feed such nonsense to
approxidate at all.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/sha1_name.c b/sha1_name.c
index 00fc415..7729925 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -399,6 +399,10 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 		unsigned long co_time;
 		int co_tz, co_cnt;
 
+		/* a @{-N} placed anywhere except the start is an error */
+		if (str[at+2] == '-')
+			return -1;
+
 		/* Is it asking for N-th entry, or approxidate? */
 		for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 			char ch = str[at+2+i];
diff --git a/t/t1508-at-combinations.sh b/t/t1508-at-combinations.sh
index 2a46af2..d5d6244 100755
--- a/t/t1508-at-combinations.sh
+++ b/t/t1508-at-combinations.sh
@@ -45,7 +45,7 @@ check "@{u}" upstream-two
 check "@{u}@{1}" upstream-one
 check "@{-1}@{u}" master-two
 check "@{-1}@{u}@{1}" master-one
-fail nonsense "@{u}@{-1}"
+nonsense "@{u}@{-1}"
 nonsense "@{1}@{u}"
 
 test_done
-- 
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