From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCHv2] Makefile: implement help target
Date: Wed, 29 Sep 2010 01:16:41 -0400
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Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Stephen Boyd <bebarino@gmail.com>,
	Andreas Ericsson <ae@op5.se>,
	Sverre Rabbelier <srabbelier@gmail.com>,
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To: Michael J Gruber <git@drmicha.warpmail.net>
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On Tue, Sep 28, 2010 at 10:38:04PM +0200, Michael J Gruber wrote:

> +help:
> +	@awk '/^# Help:/ { l=substr($$0,8); \
> +		getline; \
> +		j=index(l,":"); \
> +		print substr(l,1,j-1), substr($$0,1,index($$0,":")), substr(l,j+2); \
> +		}' <Makefile | sort | while read category target text; \
> +	do \
> +		test "$$category" = "$$currcat" || printf "$$category targets:\n"; \
> +		currcat="$$category"; \
> +		printf "    %-20s%s\n" "$$target" "$$text"; \
> +	done

Surely this is why we have perl?

help:
	@perl -n0777 \
	  -e 'push @{$$h{$$1}}, [$$3, $$2] while /^# Help: (.*?): (.*)\n(.*?):/mg;' \
	  -e 'for (sort keys(%h)) {' \
	  -e '  print "$$_:\n";' \
	  -e '  printf("    %-20s%s\n", @$$_) for (@{$$h{$$_}});' \
	  -e '}' Makefile

Note that mine will actually print the targets in a heading in the order
in which they appear in the Makefile, which I consider slightly more
useful (especially in that we can tweak the order easily). It would also
be easy to sort the headers in some more meaningful way, but here I just
did it lexically.

-Peff