run config.status with selective tags, better, docs

[subdirmk.git] / subdirmk / regen.mk.in

diff --git a/subdirmk/regen.mk.in b/subdirmk/regen.mk.in
index e2944f08ffd3f8b8f7265639e38d0ba54c1ab399..7e9f0cf108c98f45e997973f2e3ba627279e74ab 100644 (file)
--- a/subdirmk/regen.mk.in
+++ b/subdirmk/regen.mk.in
@@ -20,9 +20,19 @@ main.mk $(MAKEFILES): .makefiles.stamp ;
                $(CONFIG_STATUS)                                \
                $(top_srcdir)/Perdir.mk.in                      \
                $(foreach m,$(MAKEFILES),$(top_srcdir)/$(m).in)
-       : $? X $(filter-out Subdir.mk.in regen.mk.in, $(notdir $?))
+# 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 $?.
        ./$(CONFIG_STATUS) $(if                                 \
-               $(filter-out Subdir.mk.in regen.mk.in, $(notdir $?)),,  \
+               $(filter-out Subdir.mk.in %/Subdir.mk.in        \
+                       subdirmk/regen.mk.in                    \
+                       $(top_srcdir)/subdirmk/regen.mk.in      \
+                       , $?),,                                 \
                $(patsubst %.mk.in,%.mk,$(filter %.mk.in,$?)))
        touch $@