Improve Coverage.py configuration

Hide data files within a directory to avoid cluttering the repository root, and minimize reports.

Author: adamchainz

pyproject.toml

@@ -140,6 +140,7 @@ ini_options.xfail_strict = true
 
 [tool.coverage]
 run.branch = true
+run.data_file = ".coverage/cov"
 run.parallel = true
 run.source = [
   "django_mysql",
@@ -150,6 +151,8 @@ paths.source = [
   ".tox/**/site-packages",
 ]
 report.show_missing = true
+report.skip_covered = true
+report.skip_empty = true
 
 [tool.mypy]
 enable_error_code = [