merge: shortcircuit filemerge for identical files
- use filectx.cmp to compare files
- move merge messages into filemerge
- kill the redundant resolving message
- update tests
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)