docs: document zero bits in index "mode"

Documentation/gitformat-index.txt describes the "mode" as 32 bits, but
only documents 16 bits. Document the missing 16 bits and specify that
'unused' bits must be zero.

Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/gitformat-index.txt b/Documentation/gitformat-index.txt
index 015cb21bdc089a30e5403877ca1c61bea2b04e24..0773e5c3800392b8d4a548519b70379501207054 100644 (file)
--- a/Documentation/gitformat-index.txt
+++ b/Documentation/gitformat-index.txt
@@ -83,11 +83,13 @@ Git index format
 
   32-bit mode, split into (high to low bits)
 
+    16-bit unused, must be zero
+
     4-bit object type
       valid values in binary are 1000 (regular file), 1010 (symbolic link)
       and 1110 (gitlink)
 
-    3-bit unused
+    3-bit unused, must be zero
 
     9-bit unix permission. Only 0755 and 0644 are valid for regular files.
     Symbolic links and gitlinks have value 0 in this field.