bug#31157: Advice for help2man does not work for parallel builds

[Reuben Thomas]

On 22 April 2018 at 10:28, Mathieu Lirzin <address@hidden> wrote:

>  $(srcdir)/foo.1: foo.c foo$(EXEEXT)
>  address@hidden '$?' in \
>  *foo.c*)
>  ​​$(AM_V_P) && set -x || echo " HELP2MAN $@"; \
>  LANGUAGE= help2man --output="$(srcdir)/foo.1" ./foo$(EXEEXT);; \
>  *) : ;; \
>  esac;
>
> Nice! The one thing I don't understand: why is "-" needed at the start
> (i.e. why do we need to ignore failure of this command?).

I don't recall exactly the reason Guix added it, I guess it was to allow
the build to "succeed" even if the man pages generation failed since
that doesn't impact the software to run.  However I am not sure if it's
a good idea.

Ah, I guess it could fail because if help2man is not available. The code I supplied​ uses "missing" instead.

IIUC this case silently ignores when the ‘beetle.1’ is not distributed,

​It is distributed. This is important to cover the case where help2man is not available.​

Note that the command would not work anyway under make distcheck, as it would attempt to write to a non-writable directory, and this case is explicitly handled.

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