git-p4 unshelve: adding a commit breaks git-p4 unshelve

git-p4 unshelve uses HEAD^$n to find the parent commit, which
fails if there is an additional commit.

Signed-off-by: Luke Diamand <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: luked99

t/t9832-unshelve.sh

@@ -29,8 +29,11 @@ test_expect_success 'init depot' '
 	)
 '
 
+# Create an initial clone, with a commit unrelated to the P4 change
+# on HEAD
 test_expect_success 'initial clone' '
-	git p4 clone --dest="$git" //depot/@all
+	git p4 clone --dest="$git" //depot/@all &&
+    test_commit -C "$git" "unrelated"
 '
 
 test_expect_success 'create shelved changelist' '
@@ -77,7 +80,7 @@ EOF
 	)
 '
 
-test_expect_success 'update shelved changelist and re-unshelve' '
+test_expect_failure 'update shelved changelist and re-unshelve' '
 	test_when_finished cleanup_git &&
 	(
 		cd "$cli" &&