Merge branch 'jk/write-broken-index-with-nul-sha1'

Earlier we started rejecting an attempt to add 0{40} object name to
the index and to tree objects, but it sometimes is necessary to
allow so to be able to use tools like filter-branch to correct such
broken tree objects.

* jk/write-broken-index-with-nul-sha1:
  write_index: optionally allow broken null sha1s

1 files changed, 49 insertions, 0 deletions

diff --git a/t/t7009-filter-branch-null-sha1.sh b/t/t7009-filter-branch-null-sha1.sh
new file mode 100755
index 000000000..a997f7ac3
--- /dev/null
+++ b/t/t7009-filter-branch-null-sha1.sh
@@ -0,0 +1,49 @@
+#!/bin/sh
+
+test_description='filter-branch removal of trees with null sha1'
+. ./test-lib.sh
+
+test_expect_success 'setup: base commits' '
+	test_commit one &&
+	test_commit two &&
+	test_commit three
+'
+
+test_expect_success 'setup: a commit with a bogus null sha1 in the tree' '
+	{
+		git ls-tree HEAD &&
+		printf "160000 commit $_z40\\tbroken\\n"
+	} >broken-tree
+	echo "add broken entry" >msg &&
+
+	tree=$(git mktree <broken-tree) &&
+	test_tick &&
+	commit=$(git commit-tree $tree -p HEAD <msg) &&
+	git update-ref HEAD "$commit"
+'
+
+# we have to make one more commit on top removing the broken
+# entry, since otherwise our index does not match HEAD (and filter-branch will
+# complain). We could make the index match HEAD, but doing so would involve
+# writing a null sha1 into the index.
+test_expect_success 'setup: bring HEAD and index in sync' '
+	test_tick &&
+	git commit -a -m "back to normal"
+'
+
+test_expect_success 'filter commands are still checked' '
+	test_must_fail git filter-branch \
+		--force --prune-empty \
+		--index-filter "git rm --cached --ignore-unmatch three.t"
+'
+
+test_expect_success 'removing the broken entry works' '
+	echo three >expect &&
+	git filter-branch \
+		--force --prune-empty \
+		--index-filter "git rm --cached --ignore-unmatch broken" &&
+	git log -1 --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_done