This blog is updated daily.
A general description is here.
File-based connection functions ‘file()’, ‘gzfile()’, ‘bzfile()’, ‘xzfile()’ now signal an error when used on a directory.
‘normalizePath()’ now treats ‘NA’ path as non-existent and normalizes it to ‘NA’. ‘file.access()’ treats ‘NA’ file name as non-existent. ‘file.edit()’ and connection functions such as ‘file()’ now treat ‘NA’ file names as errors.