Merge branch 'jk/maint-null-in-trees'

We do not want a link to 0{40} object stored anywhere in our objects.

* jk/maint-null-in-trees:
  fsck: detect null sha1 in tree entries
  do not write null sha1s to on-disk index
  diff: do not use null sha1 as a sentinel value

3 files changed, 128 insertions, 0 deletions

diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 5b79c51b8c..bf7a2cd6fb 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -213,4 +213,30 @@ test_expect_success 'rev-list --verify-objects with bad sha1' '
 	grep -q "error: sha1 mismatch 63ffffffffffffffffffffffffffffffffffffff" out
 '
 
+_bz='\0'
+_bz5="$_bz$_bz$_bz$_bz$_bz"
+_bz20="$_bz5$_bz5$_bz5$_bz5"
+
+test_expect_success 'fsck notices blob entry pointing to null sha1' '
+	(git init null-blob &&
+	 cd null-blob &&
+	 sha=$(printf "100644 file$_bz$_bz20" |
+	       git hash-object -w --stdin -t tree) &&
+	  git fsck 2>out &&
+	  cat out &&
+	  grep "warning.*null sha1" out
+	)
+'
+
+test_expect_success 'fsck notices submodule entry pointing to null sha1' '
+	(git init null-commit &&
+	 cd null-commit &&
+	 sha=$(printf "160000 submodule$_bz$_bz20" |
+	       git hash-object -w --stdin -t tree) &&
+	  git fsck 2>out &&
+	  cat out &&
+	  grep "warning.*null sha1" out
+	)
+'
+
 test_done
diff --git a/t/t2107-update-index-basic.sh b/t/t2107-update-index-basic.sh
index 809fafe208..0dbbb00d74 100755
--- a/t/t2107-update-index-basic.sh
+++ b/t/t2107-update-index-basic.sh
@@ -29,4 +29,23 @@ test_expect_success 'update-index -h with corrupt index' '
 	grep "[Uu]sage: git update-index" broken/usage
 '
 
+test_expect_success '--cacheinfo does not accept blob null sha1' '
+	echo content >file &&
+	git add file &&
+	git rev-parse :file >expect &&
+	test_must_fail git update-index --cacheinfo 100644 $_z40 file &&
+	git rev-parse :file >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '--cacheinfo does not accept gitlink null sha1' '
+	git init submodule &&
+	(cd submodule && test_commit foo) &&
+	git add submodule &&
+	git rev-parse :submodule >expect &&
+	test_must_fail git update-index --cacheinfo 160000 $_z40 submodule &&
+	git rev-parse :submodule >actual &&
+	test_cmp expect actual
+'
+
 test_done
diff --git a/t/t4054-diff-bogus-tree.sh b/t/t4054-diff-bogus-tree.sh
new file mode 100755
index 0000000000..0843c87890
--- /dev/null
+++ b/t/t4054-diff-bogus-tree.sh
@@ -0,0 +1,83 @@
+#!/bin/sh
+
+test_description='test diff with a bogus tree containing the null sha1'
+. ./test-lib.sh
+
+empty_tree=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+
+test_expect_success 'create bogus tree' '
+	bogus_tree=$(
+		printf "100644 fooQQQQQQQQQQQQQQQQQQQQQ" |
+		q_to_nul |
+		git hash-object -w --stdin -t tree
+	)
+'
+
+test_expect_success 'create tree with matching file' '
+	echo bar >foo &&
+	git add foo &&
+	good_tree=$(git write-tree)
+	blob=$(git rev-parse :foo)
+'
+
+test_expect_success 'raw diff shows null sha1 (addition)' '
+	echo ":000000 100644 $_z40 $_z40 A	foo" >expect &&
+	git diff-tree $empty_tree $bogus_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'raw diff shows null sha1 (removal)' '
+	echo ":100644 000000 $_z40 $_z40 D	foo" >expect &&
+	git diff-tree $bogus_tree $empty_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'raw diff shows null sha1 (modification)' '
+	echo ":100644 100644 $blob $_z40 M	foo" >expect &&
+	git diff-tree $good_tree $bogus_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'raw diff shows null sha1 (other direction)' '
+	echo ":100644 100644 $_z40 $blob M	foo" >expect &&
+	git diff-tree $bogus_tree $good_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'raw diff shows null sha1 (reverse)' '
+	echo ":100644 100644 $_z40 $blob M	foo" >expect &&
+	git diff-tree -R $good_tree $bogus_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'raw diff shows null sha1 (index)' '
+	echo ":100644 100644 $_z40 $blob M	foo" >expect &&
+	git diff-index $bogus_tree >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'patch fails due to bogus sha1 (addition)' '
+	test_must_fail git diff-tree -p $empty_tree $bogus_tree
+'
+
+test_expect_success 'patch fails due to bogus sha1 (removal)' '
+	test_must_fail git diff-tree -p $bogus_tree $empty_tree
+'
+
+test_expect_success 'patch fails due to bogus sha1 (modification)' '
+	test_must_fail git diff-tree -p $good_tree $bogus_tree
+'
+
+test_expect_success 'patch fails due to bogus sha1 (other direction)' '
+	test_must_fail git diff-tree -p $bogus_tree $good_tree
+'
+
+test_expect_success 'patch fails due to bogus sha1 (reverse)' '
+	test_must_fail git diff-tree -R -p $good_tree $bogus_tree
+'
+
+test_expect_success 'patch fails due to bogus sha1 (index)' '
+	test_must_fail git diff-index -p $bogus_tree
+'
+
+test_done