compat: reinstate support for obsolete $(INCLUDES) variable

Since INCLUDES and AM_CPPFLAGS can be both used at the same time in a
single project, and interact in a non-obvious way, switching away from
INCLUDES is, unfortunately, not simply a matter of doing a mindless
INCLUDES -> AM_CPPFLAGS substitution.  In fact, the transition from a
"INCLUDES + CPPFLAGS" setup to a "AM_CPPFLAGS only" setup could cause
subtle bugs to sneak into the build systems of the client packages
doing the transition.  Forcing this risk upon our users is definitely
not worth the small enhancement in consistency and cleanliness that
the removal of INCLUDES would give us.

For a more extended rationale and related discussions, see:
<http://lists.gnu.org/archive/html/automake/2013-02/msg00001.html>

This change basically reverts commit v1.13-8-g880595d.

* automake.in: Re-introduce support for INCLUDES (its use will cause
warnings in the 'obsolete' category rather than fatal errors).
* doc/automake.texi: Adjust to re-add mention of INCLUDES.
* t/includes-no-more.sh: Rename ...
* t/includes-deprecation.sh: ... like this, and adjust.
* t/list-of-tests.mk: Update.
* t/warnopts.sh: Minor fixlet while at it.

Suggested-by: Peter Rosin <peda@lysator.liu.se>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/doc/automake.texi b/doc/automake.texi
index deb96d3a4..ec17160d8 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -6117,6 +6117,12 @@ files in the source directory are ignored.
 @code{AM_CPPFLAGS} is ignored in preference to a per-executable (or
 per-library) @code{_CPPFLAGS} variable if it is defined.
 
+@item INCLUDES
+This does the same job as @code{AM_CPPFLAGS} (or any per-target
+@code{_CPPFLAGS} variable if it is used).  It is an older name for the
+same functionality.  This variable is deprecated; we suggest using
+@code{AM_CPPFLAGS} and per-target @code{_CPPFLAGS} instead.
+
 @item AM_CFLAGS
 This is the variable the @file{Makefile.am} author can use to pass
 in additional C compiler flags.  In some situations, this is
@@ -6449,8 +6455,8 @@ assembly code.  This compiler must work a bit like a C compiler; in
 particular it must accept @option{-c} and @option{-o}.  The values of
 @code{CCASFLAGS} and @code{AM_CCASFLAGS} (or its per-target
 definition) is passed to the compilation.  For preprocessed files,
-@code{DEFS}, @code{DEFAULT_INCLUDES}, @code{CPPFLAGS} and
-@code{AM_CPPFLAGS} are also used.
+@code{DEFS}, @code{DEFAULT_INCLUDES}, @code{INCLUDES}, @code{CPPFLAGS}
+and @code{AM_CPPFLAGS} are also used.
 
 The autoconf macro @code{AM_PROG_AS} will define @code{CCAS} and
 @code{CCASFLAGS} for you (unless they are already set, it simply sets
@@ -6539,7 +6545,7 @@ command used is as follows:
 @table @file
 
 @item .F
-@code{$(F77) -F $(DEFS) $(AM_CPPFLAGS) $(CPPFLAGS)@*
+@code{$(F77) -F $(DEFS) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS)@*
 $(AM_FFLAGS) $(FFLAGS)}
 
 @item .r
@@ -6562,7 +6568,7 @@ is as follows:
 @code{$(F77) -c $(AM_FFLAGS) $(FFLAGS)}
 
 @item .F
-@code{$(F77) -c $(DEFS) $(AM_CPPFLAGS) $(CPPFLAGS)@*
+@code{$(F77) -c $(DEFS) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS)@*
 $(AM_FFLAGS) $(FFLAGS)}
 
 @item .r