When specifying a test with --blacklist or --whitelist with path relatives
to the repository root (eg: tests/test-check-commit.t) the file is not taken
into account. It only works when the name of the test is given.
It would be better if --blacklist and --whitelist behaviors where compatible
with --test-list.
This patch allows to use relative path with --blacklist and --whitelist
while staying compatible with the old behavior by checking the test relative
path in addition to its name.
We can just have this as another class variable.