Re: [PATCH v2 2/2] Handle more file writes correctly in shared repos

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> On Thu, 7 Jan 2016, Junio C Hamano wrote:
>
>> Johannes Schindelin <johannes.schindelin@gmx.de> writes:
>> 
>> > - git apply, when writing rejected hunks
>> 
>> Today I may try to apply and leave hello.c.rej; tomorrow you may try to
>> apply a different patch and get rejection for the same file.  And you
>> would not be able to if my umask is 077.
>
> As I just wrote in my reply to Peff: my experience with .rej files is that
> I want to inspect them, and then delete them once I addressed them. I do
> not want anybody to interfere with that, as the presence of .rej files
> serves also as a TODO list.

That argues for protecting .rej files against overwriting by myself,
too, which means (1) we do not want to loosen it by using
fopen_for_writing(), and (2) relying on permission bits and
ownership is not sufficient, i.e. just using regular fopen(3) is
wrong.

I think it is correct not to touch this codepath in this patch,
because of the above two reasons, but more simply and generally, it
is correct not to touch this codepath because core.sharedRepository
is not about working tree files, and .rej is a file you use in your
working tree.

As the log messages are often used to guide future developers, I
think the log message of this commit should mention that criterion.
It would cover multiple codepaths you listed in your proposed log
message in a more generic way, helping other people to reason about
when they see other instances of fopen(..., "w") and wonder if it
should become fopen_for_writing().

Thanks.