Re: [PATCH 2/8] Documentation/Makefile: conditionally include ../GIT-VERSION-FILE

[Junio C Hamano <gitster@pobox.com>]

Ramsay Jones <ramsay@ramsayjones.plus.com> writes:

> The 'clean' target is still noticeably slow on cygwin, despite the
> substantial improvement made by the previous patch. For example, the
> second invocation of 'make clean' below:
>
>   $ make clean >/dev/null 2>&1
>   $ make clean
>   ...
>   make[1]: Entering directory '/home/ramsay/git/Documentation'
>   make[2]: Entering directory '/home/ramsay/git'
>   make[2]: 'GIT-VERSION-FILE' is up to date.
>   make[2]: Leaving directory '/home/ramsay/git'
>   ...
>   $
>
> has been timed at 12.364s on my laptop (on old core i5-4200M @ 2.50GHz,
> 8GB RAM, 1TB HDD).
>
> Notice that the 'clean' target is making a nested call to the parent
> Makefile to ensure that the GIT-VERSION-FILE is up-to-date (prior to
> the previous patch, there would have been _two_ such invocations).
> This is to ensure that the $(GIT_VERSION) make variable is set, once
> that file had been included.  However, the 'clean' target does not use
> the $(GIT_VERSION) variable, so this is wasted effort.
>
> In order to eliminate such wasted effort, use the value of the internal
> $(MAKECMDGOALS) variable to only '-include ../GIT-VERSION-FILE' when the
> target is not 'clean'. (This drops the time down to 10.361s, on my laptop,
> giving an improvement of 16.20%).

This obviously relies on the fact that none of our build products to
be cleaned are named using $(GIT_VERSION)---in other words, if our
cleaning rule contained

	rm -f git-$(GIT_VERSION)-manual.html

this optimization would not work well.

Luckily, I think we use GIT_VERSION only to engrave version number
in the resulting document, and it does not affect the name of the
build product, so this change is safe, I think.

> Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
> ---
>  Documentation/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/Documentation/Makefile b/Documentation/Makefile
> index 652d57a1b6..5c680024eb 100644
> --- a/Documentation/Makefile
> +++ b/Documentation/Makefile
> @@ -272,7 +272,9 @@ install-html: html
>  ../GIT-VERSION-FILE: FORCE
>  	$(QUIET_SUBDIR0)../ $(QUIET_SUBDIR1) GIT-VERSION-FILE
>  
> +ifneq ($(MAKECMDGOALS),clean)
>  -include ../GIT-VERSION-FILE
> +endif
>  
>  #
>  # Determine "include::" file references in asciidoc files.