formatter: add context manager interface for convenience And port "hg files" to test it. As you can see, extra indent is necessary to port to this API. I don't think we should switch every fm.formatter() call to "with" statement.

histedit: remove now unused 'constraints' related code Now that the one action that need different logic handle that using inheritance and overriding, we can remove that code.

histedt: use inheritance to override the constraints in 'base' All actions but one actually have the same constraints when it comes to validate the 'action.node' value. So we actually just add this code to a method that can be overwritten in the one action where it matters. The now unused 'contraints' related enum and class attribute will be cleaned up in the next changeset.

histedit: move constraint verification to the 'action.verify' method Action has a method dedicated to verifying its validity. So we move code related to constrains into that method. This requires a bit more context to the 'verify' method in the same fashion we were passing the 'prev' argument. This is an extra step before we can simplify the constraint handling code further.

histedit: directly use node in 'verifyactions' It does not seem useful to convert to hex: it is an extra step and they are longer strings. So we stick to node for the logic. We only convert to short hex for error when needed. As a nice side effect this remove the explicit constant usage in'[12:]'. This will also help moving the code around later as we just have to access action.node.

histedit: temporarily shorten name of 'constraints' variable An upcoming changeset will make the line where this variable is used slightly too long. Other later changesets will clean that up further and makes the variable unnecessary, so this is only temporary and it does seems useful to put anything more complicate in place.

histedit: drop the 'nodetoverify' local variable We can just use 'action.node'.