test-revert: add case where file is added between "base" and "parent"

merge with stable

test-revert: add methodical revert to "base" with explicit file path We now also test reverting file to another revision's content. However this differs from previously introduced test by using the explicit path of each "case file" when calling revert. This should result in the same result regarding file content and backup creation, but the output of the `hg revert` call should differ.

test-revert: add methodical revert with explicit file path We now also test reverting file to the working directory parent content. However this differs from the previously introduced test by using the explicit path of each "case file" when calling revert. This should result in the same result regarding file content and backup creation, but the output of the `hg revert` call should differ.

test-revert: add methodical revert to "base" We now also test reverting s file to the content of another revision. This is still done using the `--all` flag.

test-revert: add methodical revert to parent for working directory Now that we can automatically generate states, we need to actually run revert on them and check the result. While running such tests we are checking multiple elements. The output of the `hg revert` command, the resulting content of file, and the creation of backup file. The first practical test is using the simple case `hg revert --all`, reverting all files to working directory parent content.

test-revert: display the list of all generated cases This will help to track all existing cases. (still very simple now)