revert: group action into a single dictionary We had 4 different variables to hold the list of the 4 possibles actions. I'm grouping them in a single dictionary for a few reasons. First, it makes it clearer they are all related and meant to be the final actions performed by revert. Second this simplifies the parameter of the _performrevert function. Finally the two elements in each entry (list and message) have a different consumers in different functions, this change will make it easier to split them in a later commit.

revert: add some inline comments I spend some time understanding how this part of the revert code is working. I'm adding some comments to help the code readability. I expect most of them to disappear in a coming refactoring. But the refactoring should be easier to follow with the comment.

revert: cosmetic align of the dispatch table This changeset make a minimal cosmetic change to help readability of the value in this table.