[libvirt] [PATCH 3/2] build: automate the rerun of autogen.sh

[Jim Meyering]

Eric Blake wrote:
> Automate the reuse of autogen.sh, rather than just erroring out.
>
> * cfg.mk (_update_required): Run autogen.sh, rather than just
> warning about it.
> (_autogen): New target.
> ---
>
>> > Hmm, as long as make is smart enough to warn, and now that running
>> > ./autogen.sh with no arguments is reliable at maintaining an
>> > existing setup, I could even submit a followup patch to have make
>> > blindly run ./autogen.sh instead of dying with the error that the
>> > user has to run it.  Any interest in such a followup?
>>
>> I have a slight preference for automating it.
>>
>> The current failure+instructions do serve to tell the user that something
>> unusual (and time-consuming) is about to happen, but it's easy
>> to print a warning to that effect while automating the job.
>
> This automates it.  It took me a while to figure out how to cause the
> automation without losing output - the idea in GNUmakefile of using a
> $(shell) to do a recursive make is not too good, because stdout is
> consumed and the user can't see any progress.  But the trick of adding
> a dependency on Makefile works nicely, so maybe I should rewrite
> GNUmakefile upstream in gnulib to use the same trick.

Yes ;-)

> To test the patch, I temporarily added a newline to bootstrap.conf,
> then ran 'make' twice; autogen.sh reran only on the first run of the
> two.  (Of course, reverting the temporary newline caused autogen.sh to
> rerun again - you can save yourselves that hassle by saving off
> .git-module-status before you test, and restoring it back when you
> revert bootstrap.conf back to normal).
...
> -    $(error gnulib update required; run ./autogen.sh first)
> +    $(info INFO: gnulib update required; running ./autogen.sh first)
> +Makefile: _autogen
>    endif
>  endif
>
> +.PHONY: _autogen
> +_autogen:
> +	$(srcdir)/autogen.sh
> +
>  # Exempt @...@ uses of these symbols.
>  _makefile_at_at_check_exceptions = ' && !/(SCHEMA|SYSCONF)DIR/'

Thanks!  I like it.
I've confirmed that this works as advertised.