more "main" branch fixes

Author: mr-c

Makefile

@@ -96,7 +96,7 @@ pylint_report.txt: ${PYSOURCES}
 		$^ -j0> $@ || true
 
 diff_pylint_report: pylint_report.txt
-	diff-quality --violations=pylint pylint_report.txt
+	diff-quality --compare-branch main --violations=pylint pylint_report.txt
 
 .coverage: testcov
 
@@ -116,10 +116,10 @@ coverage-report: .coverage
 	coverage report
 
 diff-cover: coverage.xml
-	diff-cover $^
+	diff-cover --compare-branch main $^
 
 diff-cover.html: coverage.xml
-	diff-cover $^ --html-report $@
+	diff-cover --compare-branch main $^ --html-report $@
 
 ## test        : run the ${MODULE} test suite
 test: FORCE