Re: [PATCH] configure.ac: move the private git m4 macro to a dedicated directory

> Git use, as many project that use autoconf, private m4 macros.
>
> When not using automake, and just relying on autoconf, the macro
> files are not picked up by default.
>
> A possibility, as git do today, is to put the private m4 macro
> in the configure.ac file, so they will copied over  the final configure
> when calling autoreconf(that call also autocon). But this makes configure.ac difficult
> to read and maintain, especially if you want to introduce new macros later.
>
> Starting from version 2.58, autoconf provide the macro AC_CONFIG_MACRO_DIR
> to declare where additional macro files are to be put and found.
> The argument passed to this macro is commonly m4.
>
> This macro, for the longest time, has been used only by libtool
> starting from version 2.0, to identify where to copy its own macro files
> when using libtoolize --copy.
>
> Starting from version 1.13, automake augments autoconf with a macro
> called AC_CONFIG_MACRO_DIRS, that provides a space-separated list
> of directories to use for looking up m4 files.
> The same macro will be available as part of autoconf 2.70,
> actually in development. Anyway also this version permit
> to use AC_CONFIG_MACRO_DIR and not need automake.
>
> Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>