This blog is updated daily.
A general description is here.
seq_along(x) is now equivalent to seq_len(length(x)) even where length() has an S3/S4 method; previously it (intentionally) always used the default method for length().
PCRE has been updated to version 7.9 (for bug fixes).
agrep() uses 64-bit ints where available on 32-bit platforms and so may do a better job with complex matches. (E.g. PR#13789, which failed only on 32-bit systems.)
seq_along(x) is now equivalent to seq_len(length(x)); previously it
was not, when x had a "surprising" length() method.
Some extreme cases of pbeta(log.p = TRUE) are more accurate (finite values < -700 rather than -Inf). (PR#13786)
pbeta() now reports on more cases where the asymptotic expansions lose accuracy (the underlying TOMS708 C code was ignoring some of these, including the PR#13786 example).
new.env(hash = TRUE, size = NA) now works, the way it has been documented to for a long time.
tcltk::tk_choose.files(multi = TRUE) produces better-formatted output with filenames containing spaces. (PR#13875)
The C utility function PrintValue no longer attempts to print attributes for CHARSXPs as those attributes are used internally for the CHARSXP cache. This fixes a segfault when calling Rf_PrintValue on a CHARSXP from C code.
Sys.glob() attempts to handle UNC paths starting with \\ (which according to the globbing rules is escaped \), thanks to a patch from Tony Plate.