Improve generated documentation handling

Author: AMDmi3

doc/CMakeLists.txt

@@ -1,12 +1,27 @@
-FILE(GLOB DOC_FILES 
-	instead.txt
+SET(DOC_FILES
 	index.html
-	instead-manual-en.html 
+)
+
+SET(GENERATED_DOC_FILES
+	instead-manual-en.html
 	instead-manual.html
 	instead-manual.pdf
 	instead-modules.pdf
+	instead.txt
 )
 
+FOREACH(FILE ${GENERATED_DOC_FILES})
+	IF(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${FILE})
+		SET(DOC_FILES ${DOC_FILES} ${FILE})
+	ELSE(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${FILE})
+		SET(MISSING_FILES ${MISSING_FILES} ${FILE})
+	ENDIF(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${FILE})
+ENDFOREACH(FILE ${GENERATED_DOC_FILES})
+
+IF(NOT "${MISSING_FILES}" STREQUAL "")
+	MESSAGE(WARNING "This distribution lacks some documentation files: ${MISSING_FILES}. These may be generated (network access and additional tools required, see doc/makepdfs), or you may use instead source tarball from sourceforge which has these files included")
+ENDIF(NOT "${MISSING_FILES}" STREQUAL "")
+
 IF(SYSTEMWIDE)
 	INSTALL(FILES ${DOC_FILES} DESTINATION ${DOCDIR})
 	INSTALL(FILES instead.6 DESTINATION ${MANDIR}/man6)