[mythtv] QString: pass by const& or value?

[Scott T]

Is it necessary to pass QString by const reference?  Specifically I'm 
looking at libmythmetadata/videometadata (converting to non-PIMPL) and 
libmyth/programinfo (some unchanged by 
https://github.com/MythTV/mythtv/commit/1a8097e3249a8ed2ea051056da08a35993bdc953 
)

If I understand correctly, passing by value increments the reference 
counter before the function call, and then using std::move just moves 
the (pointer to the) data.  Thus, passing by value is recommended for 
constructors.

Should other functions also be passed by value, due to Qt’s implicit 
sharing?  Should QStrings be returned from a function by value or const 
reference as many are in videometadata?

Thanks,
Scott