tests: make recheck

* tests/local.mk (recheck): New.

README-hacking

@@ -229,6 +229,9 @@ To run a specific set of tests, use -k (for "keyword"). For example:
 Both can be combined.
   $ make check-local TESTSUITEFLAGS='-j8 -k c++'
 
+To rerun the tests that failed:
+  $ make recheck -j5
+
 ** Typical errors
 If the test suite shows failures such as the following one
 

tests/local.mk

@@ -94,6 +94,13 @@ clean-local: clean-local-tests
 clean-local-tests:
 	test ! -f $(TESTSUITE) || $(TESTSUITE) -C %D% --clean
 
+.PHONY: recheck
+recheck: $(RUN_TESTSUITE_deps)
+	$(RUN_TESTSUITE)							\
+	  $$(perl -n								\
+	     -e 'if (/Summary of the failures/../Detailed failed tests/)'	\
+	     -e '{ /^ *[0-9]+:/ && s/:.*//s && print }' %D%/testsuite.log)
+
 check-local: $(RUN_TESTSUITE_deps)
 	$(RUN_TESTSUITE)