Muddle version 2.2 now available

I have just merged my "new_vcs" branch of muddle into trunk. This is tagged as "2_2", and thus is muddle version 2.2. Changes include:


VCS changes
The version control support has been rewritten. The actual code to write for a new version control system is now smaller, and does not rely on any particular knowledge of muddle. This should make it much easier to add a new version control system, and also simpler to maintain/extend the existing support.

Changed commands: Pull/Update replaced by Fetch/Merge
'muddle pull' and 'muddle update' are now deprecated (partly because no-one could remember what the difference between them was, and partly because different version control systems use those terms very differently). Instead we now have 'muddle fetch' and 'muddle merge'.
'muddle fetch' will pull changes from a remote repository, but will only merge those changes if it can be done with no interaction. 'muddle merge' will go ahead and do any merges, even if interaction is required. See the the help for these commands for more information.

(It is assumed that, in practice, most people will use 'muddle fetch', and that if more complex merging is required, people are likely to use the specific version control system commands to do this. However, it is conceivable that 'muddle merge' may be enough, so it is still, for the moment at least, provided.)

Note that both 'muddle fetch _all' and 'muddle merge _all' now default to processing all checkouts, and then (re)reporting any problems at the end. The old behaviour (of stopping at the first problem) is available with the '-s' or '-stop' switch.

For the moment, 'muddle pull' and 'muddle update' are both still available, but they are just aliases for 'muddle fetch'.

Changed commands: 'package' support in 'checkout' commands
Those muddle commands that expect checkout names can now also be given arguments of the form 'package:' or 'package:{role}' (and so on). Such arguments will be interpreted as "all checkouts required by the named package(s)". This means that the "dep-" and "pkg-" variants of some commands have gone away, as they are no longer needed.

Changed commands: Help
The help infrastructure has been rewritten. The main user-visible change is that help for subcommands is now available per subcommand - for instance:

muddle help query

now reports on what subcommands are available for 'query', and:

muddle help query rules

gives help for the single subcommand. See 'muddle help' for more details on how the help command works.

Changed commands: Query subcommands
Various of the query subcommands now have aliases, and in some cases what is the alias and what is the main command has been changed. See 'muddle help query' for more information.

There are some new queries: 'deployments', 'default-labels', 'default-roles' and 'package-roles'.

Internal changes
Apart from the above, the following:

• 'Dependable' has become 'Action' throughout (and similarly for all classes with Dependable in their names). All things called "dependable" have also been renamed as "action". For the moment, all the old names have been retained as aliases, in case of other code relying on them.
• The checkout tag names in utils.py have been changed, and code using them modified.
• The pkg.py::add_checkout_rules() function has been changed to fit the new command names. Things that should be transient have been made so. Various things have been simplified. In particular, 'Push' and 'Commit' no longer depend on 'CheckedOut'. This means that "muddle push" on a checkout that has not yet been checked out will no longer check it out (which sounds like a good idea).
• Since I can never remember the difference between utils.Error and utils.Failure (indeed, I tend to guess that they are the other way round than intended), they have been replaced with utils.MuddleBug and utils.GiveUp (although Error and Failure are retained as aliases for the moment, just in case other code is relying on them).
• 'pylint' and 'pyflakes' have been run over the code, and many changes (mostly minor, but a few clear bugs) have been made.
• When starting up, only the specific command that has been requested is instantiated from its class - this may give a small speedup, especially as subcommands are now split out as separate classes.
• utils.DirType is now a named tuple, and the output of 'muddle whereami' is slightly prettier.