When grep matches a line, it returns an exit code of 0, but we want it to return 1 because it means it found a broken or redirect link.

Author: stevepiercy

Makefile

@@ -189,7 +189,7 @@ linkcheck: deps  ## Run linkcheck
 
 .PHONY: linkcheckbroken
 linkcheckbroken: deps  ## Run linkcheck and show only broken links
-	cd $(DOCS_DIR) && $(SPHINXBUILD) -b linkcheck $(ALLSPHINXOPTS) $(BUILDDIR)/linkcheck | grep -wi "broken\|redirect" | GREP_COLORS='0;31' grep -vi "https://github.com/plone/volto/issues/" --color=auto || test $$? = 1
+	cd $(DOCS_DIR) && $(SPHINXBUILD) -b linkcheck $(ALLSPHINXOPTS) $(BUILDDIR)/linkcheck | GREP_COLORS='0;31' grep -wi "broken\|redirect" --color=always | GREP_COLORS='0;31' grep -vi "https://github.com/plone/volto/issues/" --color=always && if test $$? = 0; then exit 1; fi || test $$? = 1
 	@echo
 	@echo "Link check complete; look for any errors in the above output " \
 		"or in $(BUILDDIR)/linkcheck/ ."