bug#32074: maintainer-clean and removing configure/Makefile.in/etc.

[Karl Berry]

Hi - the automake manual has (for many years) said:

    @code{maintainer-clean} should not delete anything that needs to exist
    in order to run @samp{./configure && make}.
    @end itemize

    We recommend that you follow this same set of heuristics in your
    @file{Makefile.am}.

That heuristic made sense when Francois formulated it decades ago. But
nowadays, especially since autoreconf exists, it does not seem
unreasonable to me to want to delete Makefile.in, configure, etc. It is
just as easy to run autoreconf (or equivalent) as configure&&make, and
it feels nice to have such dependent files gone from the source tree,
especially when working on setting up a package with autotools.

I certainly don't suggest changing any behavior, but perhaps the manual
could mention that it could be done via maintainer-clean-local or
MAINTAINERCLEANFILES, e.g.:

MAINTAINERCLEANFILES = aclocal.m4 config.h.in configure \
                       Makefile Makefile.in */Makefile */Makefile.in

Some maintainers might prefer to also remove build-aux or more; personally
that's one step too much for me. All the more reason not to change any
code :).

Just an idea ... --best, karl.