anchor.diff:  in rec {
     # [["good/relative/source/file" true] ["bad.tmpfile" false]] -> root -> path
     filterPattern = patterns: root:
  -    (name: _type:
  -      let
  -        relPath = lib.removePrefix ((toString root) + "/") name;
  -        matches = pair: (match (head pair) relPath) != null;
  -        matched = map (pair: [(matches pair) (last pair)]) patterns;
  -      in
  -        last (last ([[true true]] ++ (filter head matched)))
  -    );
  +    let
  +      filters = map (pair: relPath: if match (head pair) relPath == null then true else last pair) patterns;
  +    in
  +      name: _type:
  +        let
  +          relPath = lib.removePrefix ((toString root) + "/") name;
  +        in foldl' (acc: f: if acc == true then f relPath else acc) true filters;
   
     # string -> [[regex bool]]
     gitignoreToPatterns = gitignore:
  
positive.code:       (filter (l: !isList l && !isComment l)
        (split "\n" gitignore));
  
    gitignoreFilter = ign: root: filterPattern (gitignoreToPatterns ign) root;
  
    # string|[string|file] (→ [string|file] → [string]) -> string
    gitignoreCompileIgnore = file_str_patterns: root:
  
negative.code:       str_patterns = map (onPath readFile) (lib.toList file_str_patterns);
      in concatStringsSep "\n" str_patterns;
  
    gitignoreFilterPure = filter: patterns: root: let
      compiledFilter = gitignoreCompileIgnore patterns root;
      filterFn = gitignoreFilter compiledFilter;
    in name: type: filterFn root name type && filter name type;
  
    # This is a very hacky way of programming this!
    # A better way would be to reuse existing filtering by making multiple gitignore functions per each root.
  