change recommended numdiff export for the regression tests

git-svn-id: https://svn.dealii.org/trunk@30232 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/tests/Makefile.rules b/tests/Makefile.rules
index 06f6b51a247634040b57ad50892da6c8fb4491eb..b918accb07b3cb075380648898c2270815a09386 100644 (file)
--- a/tests/Makefile.rules
+++ b/tests/Makefile.rules
@@ -26,7 +26,7 @@ MAIL ?= mail
 
 # this lets you overwrite the diff tool for comparisons.
 # recommended environment setting:
-#   export DEAL_II_DIFF="numdiff -a 1e-6 -q"
+#   export DEAL_II_DIFF="numdiff -a 1e-6 -q -s ' \t\n:'"
 DEAL_II_DIFF ?= diff
 
 PLATFORM = $(TARGET)+$(GXX-VERSION:intel_%=%)