Drop unused file

nix/files.nix

@@ -1,60 +0,0 @@
-{ lib
-, writeText
-, runCommand
-}:
-rec
-{
-
-  # Lists all the (relative paths to the) files in the directory.
-  listFilesInDir = dir:
-    let
-      go = dir: dirName:
-        lib.lists.concatLists
-        (
-          lib.attrsets.mapAttrsToList
-            (path: ty:
-              if ty == "directory"
-              then
-                go "${dir}/${path}" "${dirName}${path}/"
-              else
-                [ "${dirName}${path}" ]
-            )
-            (builtins.readDir dir)
-        );
-    in go dir "";
-
-  # Like nixpkgs' sourceByRegex but doesn't depend on the directory name when
-  # computing the hash. Also doesn't require matching on the dir name to
-  # actually enter the dir.
-  sourceByRegex = name: src: regexes:
-    let
-      files = builtins.filter (x: x.keep) (map mk (listFilesInDir src));
-      mk = path:
-        let relPath = lib.removePrefix (toString src + "/") (toString path);
-        in
-          { inherit relPath;
-            path = src + ("/" + path);
-            keep = lib.any (re: builtins.match re relPath != null) regexes;
-          };
-
-      files' = map (x: x.path) files;
-      paths' = map (x: x.relPath) files;
-
-      filesAbs = writeText "foo" (lib.concatStringsSep "\n" files');
-      filesRel = writeText "bar" (lib.concatStringsSep "\n" paths');
-    in
-    runCommand "source-${name}" {}
-      ''
-        mkdir -p $out
-
-        paste ${filesAbs} ${filesRel} | while IFS="$(printf '\t')" read -r f1 f2
-        do
-          f="$out/$f2"
-          mkdir -p $(dirname $f)
-          echo $f1
-          echo $f2
-          echo $f
-          cp $f1 $f
-        done
-      '';
-}