Cleanup
17-filter.t: Actually use constant sub's in tests
Repository.xs: Added cherry_pick() and revert()
21-cherrypick.t: Added cherry-pick tests
22-revert.t: Added revert tests
Index.xs: Added update_all()
Raw.xs: Added features()
Don't treat GIT_ITEROVER specially. It's a return code, not an error code
Raw.xs: Checking SvTRUE(ERRSV), no need to check count
Improved coverage