update-ref --stdin -z: deprecate interpreting the empty string as zeros

In the original version of this command, for the single case of the
"update" command's <newvalue>, the empty string was interpreted as
being equivalent to 40 "0"s.  This shorthand is unnecessary (binary
input will usually be generated programmatically anyway), and it
complicates the parser and the documentation.

So gently deprecate this usage: remove its description from the
documentation and emit a warning if it is found.  But for reasons of
backwards compatibility, continue to accept it.

Helped-by: Brad King <brad.king@kitware.com>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 15f5bfd16..2d61cceb4 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -730,10 +730,11 @@ test_expect_success 'stdin -z fails update with bad ref name' '
 	grep "fatal: invalid ref format: ~a" err
 '
 
-test_expect_success 'stdin -z treats empty new value as zeros' '
+test_expect_success 'stdin -z emits warning with empty new value' '
 	git update-ref $a $m &&
 	printf $F "update $a" "" "" >stdin &&
-	git update-ref -z --stdin <stdin &&
+	git update-ref -z --stdin <stdin 2>err &&
+	grep "warning: update $a: missing <newvalue>, treating as zero" err &&
 	test_must_fail git rev-parse --verify -q $a
 '