From: Eric Sunshine <sunshine@sunshineco.com>
Date: Tue, 19 Jan 2016 21:45:15 GMT
Subject: Re: [PATCH v4 2/2] interpret-trailers: add option for in-place editing
Message-ID: <CAPig+cRHTs9q4k=CqtY2j=ZtTYMU6_SPeCHkQe4m5AGXOjg_Ww@mail.gmail.com>
In-Reply-To: <xmqqfuxt9ti3.fsf@gitster.mtv.corp.google.com>

On Tue, Jan 19, 2016 at 3:58 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Eric Sunshine <sunshine@sunshineco.com> writes:
>> My understanding is that SANITY is an expectation that directory
>> permissions work in an expected POSIXy way: that is, a file can't be
>> deleted when its containing directory lacks 'write', and a file can't
>> be read/accessed when the directory has neither 'read' nor 'execute'.
>> This doesn't say anything about root not being allowed to read a file
>> when the file itself lacks 'read'.
>
> In short, SANITY is "does looking at permission bits sufficient to
> anticipate what the filesystem would do?" while POSIXPERM is "can
> chmod be used to tweak permission bits of the filesystem" (a
> filesystem that lacks permission bits support would qualify as
> !POSIXPERM, as there is nothing to tweak in the first place).
>
> I suspect the comment added by f400e51c and its patch description
> stressed too much about permission of a directory affecting what we
> can do to files inside the directory, and failed to describe another
> criteria for a sane environment: "files whose permission bits say
> you shouldn't be able to read or write cannot be read or written".

You suspect correctly. It was exactly the comment added by f400e51c
that misled me. (t/README does, on the other hand, mention "root", as
I noticed after reading your previous response.)

Thanks for spelling all this out. Hopefully, others reading your reply
(now and later) will be less confused than I.