Re: [PATCH v2] index-format.txt: be more liberal on what can represent invalid cache tree

Junio C Hamano [off-list ref] writes:

Nguyễn Thái Ngọc Duy  [off-list ref] writes:

quoted

 How would that work with existing versions? If you write -2 in
 cache-tree, the next time 1.8.0 updates cache tree it writes -1 back.
 That loses whatever information you attach to -2. A new cache-tree
 extension is probably better.

You can easily imagine a definition like this:
...

As we clarified that we do not allow implementations to write
anything but -1 for invalidated entries until we decide what we will
use other values for, the whole log message needs to be updated, I
think.

-- >8 --
From: Nguyễn Thái Ngọc Duy <redacted>
Date: Thu, 13 Dec 2012 08:14:47 +0700
Subject: [PATCH] index-format.txt: clarify what is "invalid"

A cache-tree entry with a negative entry count is considered "invalid"
in the current Git; it records that we do not know the object name
of a tree that would result by writing the directory covered by the
cache-tree as a tree object.

Clarify that any entry with a negative entry count is invalid, but
the implementations must write -1 there. This way, we can later
decide to allow writers to use negative values other than -1 to
encode optional information without harming interoperability; we do
not know what is encoded how, so keep these other negative values as
reserved for now.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
Signed-off-by: Junio C Hamano <redacted>
---
 Documentation/technical/index-format.txt | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt
index 9d25b30..ce28a7a 100644
--- a/Documentation/technical/index-format.txt
+++ b/Documentation/technical/index-format.txt

@@ -161,8 +161,9 @@ GIT index format
     this span of index as a tree.
 
   An entry can be in an invalidated state and is represented by having
-  -1 in the entry_count field. In this case, there is no object name
-  and the next entry starts immediately after the newline.
+  a negative number in the entry_count field. In this case, there is no
+  object name and the next entry starts immediately after the newline.
+  When writing an invalid entry, -1 should always be used as entry_count.
 
   The entries are written out in the top-down, depth-first order.  The
   first entry represents the root level of the repository, followed by the

-- 
1.8.1.rc1.141.g0ffea5d