On Sun, May 11, 2025 at 10:01:43PM +0800, shejialuo wrote: > During fsck, an empty "packed-refs" gives an error; this is unwarranted. > We should just skip checking the content of "packed-refs" just like the > runtime code paths such as "create_snapshot" which simply returns the > "snapshot" without checking the content of "packed-refs". I think this doesn't quite answer the question whether this is a _good_ idea though. The question that we need to answer is whether there are any writing code paths that may end up writing a "packed-refs" file that is completely empty. Modern Git would at least write the packed-refs header, wouldn't it? The reason why I'm a little sceptical is that there is a common problem with ext4 caused by its delayed allocation [1]. If you: 1. Write data to a temporary file. 2. Rename the file into place. 3. The host system crashes. Then it may happen that the renamed file is now completely empty. The root cause is a bug in the application: before renaming the file into place it _must_ fsync the file to disk. Git does that by default, but it is extremely easy to get wrong and we had bugs around this until ~2 years ago, if I remember correctly. We hit the problem several times in our production systems. So I wonder whether ignoring empty files would cause us to miss such a common error. But I guess if there are valid cases where we may end up with an empty "packed-refs" file we cannot do anything about it. Patrick [1]: https://thunk.org/tytso/blog/2009/03/12/delayed-allocation-and-the-zero-length-file-problem/
