- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- saves us from pointless churn
- git keeps history for us
- the year range is kept in COPYING
checksrc is updated to allow non-year using copyright statements
Closes#10205
The keyword specifies how option works when specified multiple times:
- single: the last provided value replaces the earlier ones
- append: it supports being provided multiple times
- boolean: on/off values
- mutex: flag-like option that disable anoter flag
The 'gen.pl' script then outputs the proper and unified language for
each option's multi-use behavior in the generated man page.
The multi: header is requires in each .d file and will cause build error
if missing or set to an unknown value.
Closes#9759
