From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <junkio@cox.net>
Subject: Re: [PATCH] Add ability to specify environment extension to run_command
Date: Tue, 22 May 2007 15:19:47 -0700
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Cc: git@vger.kernel.org, Sven Verdoolaege <skimo@kotnet.org>
To: Alex Riesen <raa.lkml@gmail.com>
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In-Reply-To: <20070522214754.GD30871@steel.home> (Alex Riesen's message of
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Alex Riesen <raa.lkml@gmail.com> writes:

> Others already discussed the issue. Just to be sure, I reimplemented
> that comfortable putenv with unsetenv: if an environment entry ends
> with a "=" it will be unset.

Although combination of putenv and unsetenv gives a somewhat
queasy feeling for obvious reasons, I'll let it pass.  As we
are coming up with an interface that uses only one string per
environment element, that is probably a sensible thing to do,
rather than trying to do the "historically correct" pairing of
setenv/unsetenv.

However, I do not think "VAR=" to unset it is a good interface.
Having an environment variable whose value happens to be an
empty string and not having the variable at all are two
different things.

Because you _scan_ the whole string in your patch to see if it
ends with = anyway, a trivial improvement would be to do:

	if (strchr(cmd->env, '='))
                putenv(cmd->env);
	else
        	unsetenv(cmd->env);

If you do not mind such a special syntax (e.g. "VAR="), I would
suggest doing that as a prefix (e.g. "!VAR") and do:

	if (cmd->env[0] != '!')
        	putenv(cmd->env);
	else
		unsetenv(cmd->env + 1);

The former look cleaner but less efficient; we are going to exec
so I do not think micro-optimization would matter at all, so my
suggestion would be to do the strchr().