Re: [RFC/PATCH] config: honor file permission bits

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

Patrick Steinhardt <ps@pks.im> writes:

> What I wonder is what makes our config file so special compared to
> everything else that uses lockfiles. Or put differently: if we think
> it's important to honor permissions bits (which I think is sensible),
> shouldn't we do that in a central location like in "lockfile.c" so that
> all users of this interface behave the same?

The $HOME/.gitconfig file and its XDG counterparts are the only
out-of-tree files that suffer from this issue, and being outside the
repository is what makes them special.  Theoretically, /etc/gitconfig
on a multi-user system could have the same issue, but the containing
directory would typically be read-only for regular users, which makes
the issue irrelevant there.

I do not see any sensible reason why a user would want to "protect"
in-tree files like .git/index from Git, either by running "chmod -w"
on them or by any other means.  We make files under the .git/objects/
hierarchy read-only, but that is to prevent accidental overwriting
by tools other than Git, so it does not serve as an example of Git
needing to respect read-only bits in the general lockfile machinery.

Having said all that, the patch was intentionally isolated to the
caller's side of the API, primarily because auditing all code paths
that use the lockfile API was far beyond my available time budget.