attempt to fix reftests for older versions of Coq

Makefile.coq.local

@@ -8,14 +8,20 @@ test: $(TESTFILES:.v=.vo)
 .PHONY: test
 
 COQ_TEST=$(COQTOP) $(COQDEBUG) -batch -test-mode
+REF_FILTER=egrep -v '(^Welcome to Coq|^Skipping rcfile loading.$$)'
+
+# Can't use pipes because that discards error codes and dash provides no way to control that.
+# Also egrep errors if it doesn't match anything, we have to ignore that.
+# Oh Unix...
 
 $(TESTFILES:.v=.vo): %.vo: %.v $(VFILES:.v=.vo)
 	$(SHOW)COQTOP [test] $<
 	$(HIDE)TEST="$$(basename -s .v $<)" && \
 	  TMPFILE="$$(mktemp)" && \
 	  $(TIMER) $(COQ_TEST) $(TIMING_ARG) $(COQFLAGS) $(COQLIBS) -load-vernac-source $< $(TIMING_EXTRA) > "$$TMPFILE" && \
-	  (diff -u "tests/$$TEST.ref" "$$TMPFILE" || (rm "tests/$$TEST.vo" "$$TMPFILE" && exit 1)) && \
-	  rm "$$TMPFILE"
+	  ($(REF_FILTER) < "$$TMPFILE" > "$$TMPFILE.filtered" || true) && \
+	  (diff -u "tests/$$TEST.ref" "$$TMPFILE.filtered" || rm -f "tests/$$TEST.vo" "$$TMPFILE" "$$TMPFILE.filtered") && \
+	  rm "$$TMPFILE" "$$TMPFILE.filtered"
 
 # a target, for convenience sake, to create the .ref file with the current output
 ref: $(TESTFILES:.v=.ref)
@@ -24,4 +30,6 @@ ref: $(TESTFILES:.v=.ref)
 tests/%.ref: tests/%.v $(VFILES:.v=.vo)
 	$(SHOW)COQTOP [ref] $<
 	$(HIDE)TEST="$$(basename -s .v $<)" && \
-	  $(TIMER) $(COQ_TEST) $(TIMING_ARG) $(COQFLAGS) $(COQLIBS) -load-vernac-source $< $(TIMING_EXTRA) > "tests/$$TEST.ref"
+	  $(TIMER) $(COQ_TEST) $(TIMING_ARG) $(COQFLAGS) $(COQLIBS) -load-vernac-source $< $(TIMING_EXTRA) > "tests/$$TEST.ref" && \
+	  ($(REF_FILTER) < "tests/$$TEST.ref" > "tests/$$TEST.ref.filtered" || true) && \
+	  mv "tests/$$TEST.ref.filtered" "tests/$$TEST.ref"