Include tests in the generated tarball.
# Can't use GNU tar's --transform, needs to build under Alpine Linux.
# This is a requirement for testing dist in GitLab's CI pipeline
advent-$(VERS).tar.gz: $(SOURCES) $(DOCS)
- @ls $(SOURCES) $(DOCS) | sed s:^:advent-$(VERS)/: >MANIFEST
+ @ls $(SOURCES) $(DOCS) tests | sed s:^:advent-$(VERS)/: >MANIFEST
@(ln -s . advent-$(VERS))
(tar -T MANIFEST -czvf advent-$(VERS).tar.gz)
@(rm advent-$(VERS))