This blog is updated daily.
A general description is here.
The overall default is set by environment variable ‘R_INSTALL_STAGED’. ‘R CMD INSTALL’ has new options ‘--staged-install’ and ‘--no-staged-install’, and packages can use the ‘StagedInstall’ field in their ‘DESCRIPTION’ file to opt out. (That opt-out is a temporary measure which may be withdrawn in future.)
Staged installation requires either ‘--pkglock’ or ‘--lock’, one of which is used by default.
The ‘cairo_pdf’ graphics device (and other Cairo-based devices) now clip correctly to the right and bottom border.
There was an off-by-one-pixel bug, reported by Lee Kelvin.