Documentation: add script and build target to check for broken file references

Add a simple script and build target to do a treewide grep for
references to files under Documentation, and report the non-existing
file in stderr. It tries to take into account punctuation not part of
the filename, and wildcards, but there are bound to be false positives
too. Mostly seems accurate though.

We've moved files around enough to make having this worthwhile.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/Makefile

@@ -97,6 +97,9 @@ endif # HAVE_SPHINX
 # The following targets are independent of HAVE_SPHINX, and the rules should
 # work or silently pass without Sphinx.
 
+refcheckdocs:
+	$(Q)cd $(srctree);scripts/documentation-file-ref-check
+
 cleandocs:
 	$(Q)rm -rf $(BUILDDIR)
 	$(Q)$(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media clean
@@ -109,6 +112,7 @@ dochelp:
 	@echo  '  epubdocs        - EPUB'
 	@echo  '  xmldocs         - XML'
 	@echo  '  linkcheckdocs   - check for broken external links (will connect to external hosts)'
+	@echo  '  refcheckdocs    - check for references to non-existing files under Documentation'
 	@echo  '  cleandocs       - clean all generated files'
 	@echo
 	@echo  '  make SPHINXDIRS="s1 s2" [target] Generate only docs of folder s1, s2'

Makefile

@@ -1454,7 +1454,8 @@ $(help-board-dirs): help-%:
 
 # Documentation targets
 # ---------------------------------------------------------------------------
-DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs linkcheckdocs dochelp
+DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs \
+	       linkcheckdocs dochelp refcheckdocs
 PHONY += $(DOC_TARGETS)
 $(DOC_TARGETS): scripts_basic FORCE
 	$(Q)$(MAKE) $(build)=Documentation $@

scripts/documentation-file-ref-check

@@ -0,0 +1,15 @@
+#!/bin/sh
+# Treewide grep for references to files under Documentation, and report
+# non-existing files in stderr.
+
+for f in $(git ls-files); do
+	for ref in $(grep -ho "Documentation/[A-Za-z0-9_.,~/*+-]*" "$f"); do
+		# presume trailing . and , are not part of the name
+		ref=${ref%%[.,]}
+
+		# use ls to handle wildcards
+		if ! ls $ref >/dev/null 2>&1; then
+			echo "$f: $ref" >&2
+		fi
+	done
+done