Add listbyfile option

tag.sh

@@ -345,6 +345,11 @@ main() {
         listtags "$2"
         exit 0
     fi 
+
+    if [[ "$1" = "listbyfile" ]]; then
+        sqlite_query "SELECT id,filename FROM files" |\
+         fzf --delimiter="|" --preview "sqlite3 $DB_FILE 'SELECT label FROM tags WHERE id IN (SELECT tid FROM tags_ties WHERE fid ={2})'"
+    fi
 }
 
 main "$@"