Release 2.2.0 CHANGES: - Incremental local confluence checking for non higher-order and non AC rules. - Add options -o hrs and -o xtc to the export command. - `whnf` function takes a problem as argument and a list of tags that configure the rewriting. Tags may block beta reduction, block definition expansion or block rewriting. - Do not print empty term environments `.[]`. - Allow users to use the pattern variables `$0`, `$1`, etc. and internally name pattern variables by their index. - Fixed debug flag printing in Pretty. - Compatibility with Cmdliner 1.1.0 and Bindlib 6.0.0. - `tree_walk` is no longer in the API