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
Checking encoding (ascii)...
Checking extensions...
Checking templates...
Checking patch...
Checking merge helper...
Checking commit editor...
Checking username...
No problems detected