Set up basic framework for common testing scenarios.

Tests for

• tags
• branches
• Merging
• multiple heads
• binary files
• file names with:
  • spaces
  • URL/XML entities, \, %, ! etc
  • non-ascii characters
• copies/moves
• deletions
• merges with no content: merges where there is no clashes - all changes on each branch are to separate files
• case-insensitive filesystems, pulling a change with a case change in it.
• loc, per-author loc
• Merge commits with no changeset
• Permission changes, by themselves, combined with modification, copy, move
• file changes to directory/symlink & vice-versa