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Date:   Thu, 8 Dec 2016 13:53:27 -0500
From:   Jeff King <peff@peff.net>
To:     vi0oss <vi0oss@gmail.com>
Cc:     Stefan Beller <sbeller@google.com>,
        "git@vger.kernel.org" <git@vger.kernel.org>,
        Stefan Beller <stefanbeller@gmail.com>
Subject: Re: [PATCH] submodule--helper: set alternateLocation for cloned
 submodules
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On Thu, Dec 08, 2016 at 09:04:46PM +0300, vi0oss wrote:

> Why Git test use &&-chains instead of proper "set -e"?

Because "set -e" comes with all kinds of confusing corner cases. Using
&& chains is annoying, but rarely surprising.

One of my favorite examples is:

  set -e
  (
    false
    echo 1
  ) || {
    echo outcome=$?
    false
  }
  echo 2

which prints both "1" and "2".

Inside the subshell, "set -e" has no effect, and you cannot re-enable it
by setting "-e" (it's suppressed entirely because we are on the
left-hand side of an || conditional).

So you could write a function like this:

  foo() {
    do_one
    do_two
  }

that relies on catching the failure from do_one. And it works here:

  set -e
  foo

but not here:

  set -e
  if foo then
    do_something
  fi

And there's no way to make it work without adding back in the
&&-chaining.

-Peff