Re: [PATCH 29/29] t/test-lib: teach --chain-lint to detect broken &&-chains in subshells

On Tue, Jun 26, 2018 at 5:01 PM Jeff King [off-list ref] wrote:

On Tue, Jun 26, 2018 at 04:46:18PM -0400, Eric Sunshine wrote:

quoted

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.