Merge branch 'mm/keyid-docs' into maint

Very small number of options take a parameter that is optional (which is not a great UI element as they can only appear at the end of the command line). Add notice to documentation of each and every one of them. * mm/keyid-docs: Documentation: explain optional arguments better Documentation/grep: fix documentation of -O Documentation: use 'keyid' consistently, not 'key-id'