Version Control Refactoring

This branch is a sandbox for introducing new features that are potentially disruptive.

This is based on the previous refactoring and on the TracDiff branch, both of them pretty much stable and already integrated in the trunk for milestone:0.10.

The forthcoming changes aim to be better support some advanced version control system backends, like ​Mercurial. To that effect, the changes added to the core will be exercised by jointly developing the TracMercurial plugin.

See also the related ​thread on the Trac Devel mailing list.

Support for Multiple scopes within a Repository

This basically means fixing #1830. Initial work on this in r2992.

Support for Mercurial-like Version Control System

Basic Level

• DONE
  • support for non-numerical changesets (start with hexadecimal digit support)
  • support for extra changeset properties

Those are the minimal changes needed so that the Mercurial plugin can work at all.

Advanced Level

• Support for direct jump to a tag or a branch
• DONE
  • Support for arbitrary changeset names (e.g. [tip] or [head])

Support for Big Repositories

This means extended cache support, and certainly needs some big changes to the way caching is done.