Re: [PATCH 22/24] Let usage() take a printf-style format

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 10, 2009, 20:16 UTC
Message-ID: <7veio66spc.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1257779104-23884-22-git-send-email-jrnieder@gmail.com>

Jonathan Nieder <jrnieder@gmail.com> writes:

> merge-recursive and diff --no-index are not able to use usage()
> because their usage strings depend on the circumstances in which
> they are called.

Since die() and warn() are already printf-like, it may be tempting to do this, but this is wrong.

I do not want to vet all the existing call sites to usage() of make sure that all of them _happen_ to pass constant strings that do not have any '%' in them.

Much more importantly, without a patch to future-proof all existing callsites to modify from

	usage(blame_usage);

to

	usage("%s", blame_usage);

everybody needs to remember that some *_usage strings are special and have to double % in it forever, which is a maintenance nightmare.

Besides, the majority of usage strings are _expected_ to be constant. That is an important difference from die/warn whose purpose is to diagnose and give appropriate message to the situation (hence they benefit from formatting).

I've renamed this to usagef() and updated your two callers to use it in the version I queued to 'pu'.

Thanks.