Merge branch 'maint-1.5.6' into maint-1.6.0

* maint-1.5.6:
  revision traversal and pack: notice and die on missing commit

revision.c

@@ -1538,14 +1538,16 @@ static struct commit *get_revision_1(struct rev_info *revs)
 			    (commit->date < revs->max_age))
 				continue;
 			if (add_parents_to_list(revs, commit, &revs->commits, NULL) < 0)
-				return NULL;
+				die("Failed to traverse parents of commit %s",
+				    sha1_to_hex(commit->object.sha1));
 		}
 
 		switch (simplify_commit(revs, commit)) {
 		case commit_ignore:
 			continue;
 		case commit_error:
-			return NULL;
+			die("Failed to simplify parents of commit %s",
+			    sha1_to_hex(commit->object.sha1));
 		default:
 			return commit;
 		}

t/t5307-pack-missing-commit.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+
+test_description='pack should notice missing commit objects'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	for i in 1 2 3 4 5
+	do
+		echo "$i" >"file$i" &&
+		git add "file$i" &&
+		test_tick &&
+		git commit -m "$i" &&
+		git tag "tag$i"
+	done &&
+	obj=$(git rev-parse --verify tag3) &&
+	fanout=$(expr "$obj" : "\(..\)") &&
+	remainder=$(expr "$obj" : "..\(.*\)") &&
+	rm -f ".git/objects/$fanout/$remainder"
+'
+
+test_expect_success 'check corruption' '
+	test_must_fail git fsck
+'
+
+test_expect_success 'rev-list notices corruption (1)' '
+	test_must_fail git rev-list HEAD
+'
+
+test_expect_success 'rev-list notices corruption (2)' '
+	test_must_fail git rev-list --objects HEAD
+'
+
+test_expect_success 'pack-objects notices corruption' '
+	echo HEAD |
+	test_must_fail git pack-objects --revs pack
+'
+
+test_done