Add make target to generate compatibility patches

Simplifying what's required from contributors to help us in this
project.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: test test-report test-fix
+.PHONY: test test-report test-fix update-compatibility-patch
 
 PHP_74_OR_NEWER=`php -r "echo (int) version_compare(PHP_VERSION, '7.4', '>=');"`
 
@@ -15,5 +15,12 @@ test-fix: vendor
 	@vendor/bin/phpcbf tests/input2; diff tests/input2 tests/fixed; if [ $$? -ne 0 ]; then rm -rf tests/input2/ && if [ $(PHP_74_OR_NEWER) -eq 1 ]; then git apply -R tests/php-compatibility.patch; fi; exit 1; fi
 	@rm -rf tests/input2/ && if [ $(PHP_74_OR_NEWER) -eq 1 ]; then git apply -R tests/php-compatibility.patch; fi
 
+update-compatibility-patch:
+	@git apply tests/php-compatibility.patch
+	@echo -e "Please open your editor and apply your changes\n"
+	@until [ "$${compatibility_resolved}" == "y" ]; do read -p "Have finished your changes (y|n)? " compatibility_resolved; done && compatibility_resolved=
+	@git diff -- tests/expected_report.txt tests/fixed > .tmp-patch && mv .tmp-patch tests/php-compatibility.patch && git apply -R tests/php-compatibility.patch
+	@git commit -m 'Update compatibility patch' tests/php-compatibility.patch
+
 vendor: composer.json
 	composer update