test-revert: reverting no change means it's clean This is the first step in a series that aims to put the state, not the state transitions, in the filenames of the files generated by the gen-revert-cases.py script. The possible state of a file in a revision and in the working copy is only whether it exists and what its content is (the tests don't care check flags). In the dirstate, the only state is whether it's tracked or not. With the new naming, the file that is currently called modified_untracked-clean now becomes content1_content2_content2-untracked, for example. By putting these states in the filename, it becomes easier to see that we're not missing or duplicating any state, and to check that the state is what we think it is. For example, the file that is currently called missing_clean becomes missing_missing_missing-tracked and it's clearer that it should be tracked. Putting the content in the filename will also make the tests of file content (e.g. "cat ../content-parent.txt") very obvious. When we put the state in the filename, the filenames clearly need to be unique. However, it turns out that some states are currently tested multiple times. The 'revert' transition in the script means to take the content from the grandparent. If the parent is the same as the grandparent, there is no change compared to the parent, which is exactly what 'clean' means. Avoid testing the same state twice.