Add diff-cover

Signed-off-by: Bernát Gábor <[email protected]>

Author: gaborbernat

setup.cfg

@@ -42,6 +42,7 @@ where = src
 testing =
     covdefaults>=2
     coverage>=6
+    diff-cover>=6.4
     pytest>=6
     pytest-cov>=3
     sphobjinv>=2

tox.ini

@@ -27,6 +27,7 @@ commands =
       --cov-config=setup.cfg --no-cov-on-fail --cov-report term-missing:skip-covered --cov-context=test \
       --cov-report html:{envtmpdir}{/}htmlcov --cov-report xml:{toxworkdir}{/}coverage.{envname}.xml \
       tests}
+    diff-cover --compare-branch {env:DIFF_AGAINST:origin/main} {toxworkdir}{/}coverage.{envname}.xml
 package = wheel
 wheel_build_env = .pkg