dirstate: refactor granularity code, add a test
- rename option dirstate.granularity
- move option reading into .write()
- add a simple test
#!/bin/sh
hg init
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1