Resurrect the 'rules' tool.

This tool is useful for writing shell completion script for tools
expecting a rule name as argument.

The tool was dropped by 34b46f28c.

Fix #1024.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/eval_env.h b/src/eval_env.h
index 999ce42..8fb9bf4 100644
--- a/src/eval_env.h
+++ b/src/eval_env.h
@@ -33,8 +33,13 @@ struct Env {
 /// A tokenized string that contains variable references.
 /// Can be evaluated relative to an Env.
 struct EvalString {
+  /// @return The evaluated string with variable expanded using value found in
+  ///         environment @a env.
   string Evaluate(Env* env) const;
 
+  /// @return The string with variables not expanded.
+  string Unparse() const;
+
   void Clear() { parsed_.clear(); }
   bool empty() const { return parsed_.empty(); }