We have been writing -1 as "invalid" since day 1. On that same day we
accept all negative entry counts as "invalid". So in theory all C Git
versions out there would be happy to accept any negative numbers. JGit
seems to do exactly the same.
Correct the document to reflect the fact that -1 is not the only magic
number. At least one implementation, libgit2, is found to treat -1
this way.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
---
On Thu, Dec 13, 2012 at 1:14 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes:
>
>> We have been writing -1 as "invalid" since day 1. On that same day we
>> accept all negative entry counts as "invalid". So in theory all C Git
>> versions out there would be happy to accept any negative numbers. JGit
>> seems to do exactly the same.
>
> I am of two minds here.
>
> The existing code is being more lenient than specified when they
> read stuff others wrote, but it still adheres to -1 when writing.
> Allowing random implementations to write random negative values will
> close the door for us to later update the specification to encode
> more informatin about these invalid entries by using negative value
> other than -1 here.
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.
> I am OK with a reword to say "negative means invalid, and writers
> should write -1 for invalid entries", but without the latter half,
> this change is not justified.
Done.
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
--
1.8.0.rc2.23.g1fb49df
--
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