bug#59099: 3-rd party aux files.

[Van de Bugger]

> If you, or anyone, can draft a patch, that would be great.

I think I could draft a patch, but I am not sure which interface to
choose for the new feature. I see few possible approaches:


1. Let automake look for aux files in *two* directories:
/usr/share/automake-1.16 and /usr/share/automake. In such case, the --
libdir option (and/or the AUTOMAKE_LIBDIR environment variable) will
replace the first dir (versioned one), the second dir (unversioned one)
is always searched for aux files.

This option looks good because automake uses similar approach when
searching for *.m4 files: it searches in /usr/share/aclocal-1.16 first,
then in /usr/share/aclocal. Disadvantage is that both directories are
not writable by non-privileged user.


2. Let automake maintain the *list* of directories to be searched for
aux files. In such case, the --libdir  option (and the AUTOMAKE_LIBDIRS
environment variable) will insert the given directory to the beginning
(or to the end?) of the list. Multiple --libdir options are allowed.

Such approach looks good because non-privileged user can specify his
own aux directory. However, I worry about backward compatibility. Is
there any existing code relying on the fact that automake ignores
standard directory if the --libdir option is specified? It seems the --
libdir option is rarely used (manual states it is used primarily for
debugging), but I am not sure.


3. A combination of 1 and 2 is also possible. automake can maintain the
list of directories to be searched, which is initialized to
(/usr/share/automake-1.16, /usr/share/automake). The first directory
contains files provided by automake, the second — system-wide third-
party files, while non-privileged user is able to specify personal
directory in addition to system-wide directories either by the --libdir
option or by the AUTOMAKE_LIBDIRS environment variable.


Also, it is not clear to me, should it affect searching for *.am files
or not.

Any comments?


> ...my automake time is woefully scarce at the moment :(.

Not a problem, there is no hurry.

Thanks.