demo/{cal,retry}.should: new example

demo/cal.should

@@ -37,3 +37,14 @@ w7: 31
 
 $ 11 months have 30 days or more
 w11: 30
+
+
+# A test with 'f' is expected to be failed
+
+$ The year is 1999, but this is not working now
+f: 1999
+
+# A test with 'f' but that nevertheless passes triggers a warning
+
+$ The year is 2001, this should not work now... but yes
+f: 2001

demo/retry.should

+# should.py --retry relaunches the previous failed or warned tests,
+# with the same options that at the first call.
+
+python3 src/should.py -v demo/hello.should demo/cal.should
+python3 src/should.py --retry
+
+$ 'cal.should' was labeled as 'TODO-but-ok' at both calls
+rl: files with.*TODO-but-ok.*demo/cal.should.*Retrying
+rl: Retrying .*files with.*TODO-but-ok.*demo/cal.should
+
+$ At the second call, 'cal.should' is tested, but not 'hello.should'
+r0l: Retrying .* demo/hello.should
+r1l: Retrying .* demo/cal.should
+
+$ The option '-v' was used at both calls
+rl: 7 months have 31 days.*Retrying
+rl: Retrying.*7 months have 31 days
+