Re: [PATCH v3] sha1_file: pass empty buffer to index empty file

[Jeff King <peff@peff.net>]

On Tue, May 19, 2015 at 11:11:38AM -0700, Junio C Hamano wrote:

> Subject: [PATCH] copy.c: make copy_fd() report its status silently
> 
> When copy_fd() function encounters errors, it emits error messages
> itself, which makes it impossible for callers to take responsibility
> for reporting errors, especially when they want to ignore certaion
> errors.
> 
> Move the error reporting to its callers in preparation.
> [...]

Looks good to me. And thank you for being thorough in analyzing the
impact on all the callers.

>  - hold_lock_file_for_append(), when told to die on error, used to
>    exit(128) relying on the error message from copy_fd(), but now it
>    does its own die() instead.  Note that the callers that do not
>    pass LOCK_DIE_ON_ERROR need to be adjusted for this change, but
>    fortunately there is none ;-)

Not related to your patch, but I've often wondered if we can just get
rid of hold_lock_file_for_append. There's exactly one caller, and I
think it is doing the wrong thing. It is add_to_alternates_file(), but
shouldn't it probably read the existing lines to make sure it is not
adding a duplicate? IOW, I think hold_lock_file_for_append is a
fundamentally bad interface, because almost nobody truly wants to _just_
append.

And I have not investigated it carefully, but I suspect that we do not
even have to be that careful. The only time we write the file is during
clone, and I suspect we could just use a string_list, and then write it
out. We probably don't even need to lock (it's not like we take a lock
before creating the "objects" directory in the first place).

Anyway, end mini-rant. It is probably not hurting anyone and does not
need to be dealt with anytime soon.

-Peff