git add --intent-to-add: fix removal of cached emptiness

This uses the extended index flag mechanism introduced earlier to mark
the entries added to the index via "git add -N" with CE_INTENT_TO_ADD.

The logic to detect an "intent to add" entry for the purpose of allowing
"git rm --cached $path" is tightened to check not just for a staged empty
blob, but with the CE_INTENT_TO_ADD bit.  This protects an empty blob that
was explicitly added and then modified in the work tree from being dropped
with this sequence:

	$ >empty
	$ git add empty
	$ echo "non empty" >empty
	$ git rm --cached empty

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/t/t3600-rm.sh b/t/t3600-rm.sh
index 5b4d6f7138..b7d46e50a8 100755
--- a/t/t3600-rm.sh
+++ b/t/t3600-rm.sh
@@ -187,8 +187,8 @@ test_expect_success 'but with -f it should work.' '
 	test_must_fail git ls-files --error-unmatch baz
 '
 
-test_expect_failure 'refuse to remove cached empty file with modifications' '
-	touch empty &&
+test_expect_success 'refuse to remove cached empty file with modifications' '
+	>empty &&
 	git add empty &&
 	echo content >empty &&
 	test_must_fail git rm --cached empty