Re: git bugs

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 12, 2008, 20:06 UTC
Message-ID: <7v4p7y1kqu.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <alpine.LFD.1.10.0806101028040.3101@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> writes:

> The other approach is to know that an empty blob always has a very 
> specific SHA1. Here's an trial patch.

Show 20 quoted lines

>  read-cache.c |   16 ++++++++++++++++
>  1 files changed, 16 insertions(+), 0 deletions(-)
>
> diff --git a/read-cache.c b/read-cache.c
> index 8e5fbb6..f83de8c 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> ...
> @@ -193,6 +203,12 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
>  	if (ce->ce_size != (unsigned int) st->st_size)
>  		changed |= DATA_CHANGED;
>  
> +	/* Racily smudged entry? */
> +	if (!ce->ce_size) {
> +		if (!is_empty_blob_sha1(ce->sha1))
> +			changed |= DATA_CHANGED;
> +	}
> +
>  	return changed;
>  }

Thanks.  This would be a good fix to the issue.

The only theoretical worry I can think of is if there is an insane convert_to_worktree() filter that turns a non-empty blob into an empty work tree file.

An "In blobs, always store everything as UTF16 with BOM" filter, when badly implemented, might turn an empty work tree file into a blob with BOM and nothing else in it, but we can safely declare that such use case is simply insane and broken ;-).