Now that all known format variants exists outside of the function, we can gather
them in a lists. This build a single entry point other code can use (current
target: extensions).
The repository upgrade code is updated to simply use entries from this list.
As a side effect this will also allow extensions to register their own format
variants, to do this "properly" we should introduce a "registrar" for this
category of object. However I prefer to keep this series simple, and that will
be adventure for future time.
Our goal here is to get top level definition for all the format variants. Having
them defined outside of the function enabled other users of that logic.
They are two keys components of a format variant:
1) the name and various descriptions of its effect,
2) the code that checks if the repo is using this variant and if the config
enables it.
That second items make us pick a class-based approach, since different variants
requires different code (even if in practice, many can reuse the same logic).
Each variants define its own class that is then used like a singleton. The
class-based approach also clarify the definitions part a bit since each are
simple assignment in an indented block.
The 'fromdefault' and 'fromconfig' are respectively replaced by a class
attribute and a method to be called at the one place where "fromconfig"
matters.
Overall, they are many viable approach for this, but this is the one I picked.
The 'deficiency' type has multiple specificities. We create a dedicated class to
host them. More logic will be added incrementally in future changesets.
Through the code, we use a mix of 'improvement' object and string. Having a
single type would be simpler. For this we need the object to be comparable.
This sounds like higher level logic to process arguments.
Moving it out of 'determineactions' will allow passing only deficiencies to the
function. Then, in a future changeset, we will remove dispatch on "improvement
type" within the function. See next changeset for details.
Since we already have the list of optimisations independent from the
deficiencies, we can use it directly.
(we make a dual assignement in this changeset to simplify the next one)
Our ultimate goal is to make it easier to get a diagnostic of the repository
format. A first important and step for that is to separate part related to
repository format from the optimisation. We start by having two different
functions returning the two categories of possible "improvement".
Given about 2/3 or 'mercurial.repair' is now about repository upgrade, I think
it is fair to move it into its own module.
An expected benefit is the ability to drop the 'upgrade' prefix of many
functions. This will be done in coming changesets.
