;Shake webmanuals: add a "generated by" comment (hledger_site/#10)

[ci skip]

Shake.hs

@@ -331,15 +331,21 @@ main = do
                       in if "hledger_" `isPrefixOf` h
                          then drop 8 h ++ " format"
                          else h
-      -- assume all other m4 files in dir are included by this one XXX not true in hledger-lib
-      deps <- liftIO $ filter (/= src) . filter (".m4.md" `isSuffixOf`) . map (dir </>) <$> S.getDirectoryContents dir
-      need $ [src, commonm4, packagem4] ++ deps
+      -- assume any other m4 files in dir are included by this one XXX not true in hledger-lib
+      subfiles <- liftIO $ filter (/= src) . filter (".m4.md" `isSuffixOf`) . map (dir </>) <$> S.getDirectoryContents dir
+      let deps = [src, commonm4, packagem4] ++ subfiles
+      need deps
       when (manual=="hledger") $ need commandmds
       -- add the web page's heading.
       -- XXX Might be nice to do this atomically with the below, so
       -- make avoid any double refresh when watch docs with entr/livereload.
       -- But cmd Shell doesn't handle arguments containing spaces properly.
-      liftIO $ writeFile out $ "# " ++ heading ++ "\n\n"
+      liftIO $ writeFile out $ unlines [
+         "<!-- " ++ "Generated by \"Shake webmanuals\" from " ++ unwords deps ++ " -->"
+        ,""
+        ,"# " ++ heading
+        ,""
+        ]
       cmd Shell
         "m4 -P -DMAN -DWEB -I" dir commonm4 packagem4 src "|"
         pandoc fromsrcmd towebmd