+# This filtering arranges that we can often run config.status to
+# generate only particular output files. We look for *inputs* that
+# have changed. If the only inputs that have changed are ones that we
+# know affect only one output (Subdir.mk.in and regen.mk.in), we pass
+# config.status the corresponding output file names. Otherwise we
+# pass nothing and config.status does them all. We need to mention
+# regen.mk.in twice because if $(top_srcdir) is `.', make elides the
+# directory part from $?.