Links the bookmark file into the users local surfraw configuration.
#If the file already exists, force overwrite only if symlinked files hash
#matches the already existing file.
home.activation.linkSurfrawBookmarkFile = let
  placeholderBookmarkFile = pkgs.buildPackages.writeText
    "surfraw-placeholder-bookmarks" ''
    # This is a readonly, example bookmark file generated by home-manager.
    # If you want your own bookmarks here, use the 'linkBookmarkFile'
    # option of the surfraw module. This example file will then be replaced
    # by a link to your specified bookmark file.
    #
    # Bookmark Format
    # ---------------
    #
    # Everything after a # is treated as comment until the end of line.
    # Bookmarks are given in following form.
    # <name><whitespace><url> #And possible some tags as a comment
    # ntk http://www.ntk.net/
  '';
  source = if cfg.linkBookmarkFile == null
    then placeholderBookmarkFile else toString cfg.linkBookmarkFile;
  target = "${config.xdg.configHome}/surfraw/bookmarks";
  hashOf = file: builtins.hashFile "sha256" file;
  isSourceAlsoTarget = hashOf source == hashOf target;
  isTargetPlaceholder = hashOf target == hashOf placeholderBookmarkFile;
in lib.hm.dag.entryAfter ["writeBoundary"]
  (if !(pathExists target) || isTargetPlaceholder || isSourceAlsoTarget
  then "$DRY_RUN_CMD ln -s -f $VERBOSE_ARG ${source} ${target}"
  else "$DRY_RUN_CMD ln -s $VERBOSE_ARG ${source} ${target}");