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.

revert: add a test case to reverting "add" during merges This kind of revert is specifically trickier since the file is reported as "modified" by status. This case was only tested by some largefiles test. We introduce proper testing of all aspects of this case in the revert tests themselves.