Add a pointer to "hg -v help" to the bottom of hg help {,cmd} output
This should make it easier to discover global options.
As a bonus, they are no longer displayed by something like a
hg -v help dates
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
abort: Permission denied: test-ro-message/b/vehicle