This form allows you to request diffs between any two revisions of this file. For each of the two "sides" of the diff, [if-any tags] select a symbolic revision name using the selection box, or choose 'Use Text Field' and enter a numeric revision. [else] enter a numeric revision. [end]

  [for diff_select_hidden_values][end] Diffs between [if-any tags] [else] [end] and [if-any tags] [else] [end]
  Type of Diff should be a