Re: [PATCH] doc: filter-branch does not require re-export of vars

From: Jeff King <peff@peff.net>
Date: May 26, 2017, 18:37 UTC
Message-ID: <20170526183702.jrjkykhldz74pquq@sigill.intra.peff.net>
In-Reply-To: <20170526173654.4238-1-asheiduk@gmail.com>

On Fri, May 26, 2017 at 07:36:54PM +0200, Andreas Heiduk wrote:

> The function `set_ident` in `filter-branch` exported the variables
> GIT_(AUTHOR|COMMITTER)_(NAME|EMAIL|DATE) at least since 6f6826c52b in 2007.
> Therefore the filter scripts don't need to re-eport them again.

Some old shells keep separate values for the internal and exporter versions of variables. I.e., this:

  foo=one
  export foo
  foo=two

would continue to export $foo as "one", even though it is "two" inside the script.

However, I think POSIX mandates the behavior you'd expect. And the only shell I know that misbehaves in this way is Solaris /bin/sh, which we have already declared too broken to support. According to

  https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Limitations-of-Builtins.html#export

it sounds like there are some other antique shells which may do the same (it doesn't cover this case explicitly, but the "coexist" cases it mentions are likely to behave in this way).

At this point, I'd be inclined to remove the text as you suggest and either make a small note at the bottom of the page, or just omit it entirely and assume that anybody on an old non-POSIX shell can fend for themselves.

-Peff