- add writepending to flush delayed writes to separate file
- add support in hooks for lazy evaluation of callable parameters
- add HG_PENDING to pretxn hooks
- call writepending if hook is used
- pass repo root to hook environment
- if HG_PENDING = repo root, we're in pretxn hook
- read pending data to make pending changesets visible
- filter HG_PENDING in tests/printenv.py