From: Eric Sunshine <sunshine@sunshineco.com>
Date: Tue, 26 Jun 2018 21:13:05 GMT
Subject: Re: [PATCH 29/29] t/test-lib: teach --chain-lint to detect broken &&-chains in subshells
Message-ID: <CAPig+cRzZ-Nd2b-M8v0NUsLX_gkKwLqyakgcRhwGf3CzsWwxBA@mail.gmail.com>
In-Reply-To: <20180626210100.GA3682@sigill.intra.peff.net>

On Tue, Jun 26, 2018 at 5:01 PM Jeff King <peff@peff.net> wrote:
> On Tue, Jun 26, 2018 at 04:46:18PM -0400, Eric Sunshine wrote:
> > Some of these dangers can be de-thoothed during the linting phase by
> > defining do-nothing shell functions:
> >
> >     cp () { :; }
> >     mv () { :; }
> >     ln () { :; }
> >
> > That, at least, makes the scariest case ("rm") much less so.
>
> Now that's an interesting idea. We can't catch every dangerous action
> (notably ">" would be hard to override), but it should be pretty cheap
> to cover some obvious ones.

Taking the idea a bit further, the 'sed' script could also throw away
strings of "../" inside subshells, which would help defang the more
difficult cases, like "echo x >../git.c". There are pathological
cases, of course, which it wouldn't catch:

    P=../git.c
    test_expect_success 'foo' '
        (
            cd dir &&
            echo x >$P
        )
    '

but it does help mitigate the issue for the most typical cases.