NEW FEATURES:

• tools::Rdiff(useDiff = TRUE) checks for the presence of an
  external diff command and switches to useDiff = FALSE if none is
  found. This allows R CMD Rdiff to always work.

• On Windows, environment variable R_LIBCURL_SSL_REVOKE_BEST_EFFORT
  can be used to switch to only ‘best-effort’ SSL certificate
  revocation checks with the default "libcurl" download method.
  This reduces security, but may be needed for downloads to work
  with MITM proxies (PR#18379).

• (macOS) The run-time check for libraries from XQuartz for X11 and
  Tcl/Tk no longer uses otool from the Apple Developer Tools
  (PR#18400).

• The LaTeX style for producing the PDF manuals, Rd.sty, now loads
  the standard amsmath, amsfonts and amssymb packages for greater
  coverage of math commands in the Rd \eqn and \deqn macros. The
  \mathscr LaTeX command is also provided (via the mathrsfs
  package, if available, or the amsfonts bundle otherwise),
  fulfilling the wish of PR#18398.

• (Windows) The default format of readClipboard() and
  writeClipboard() has been changed to 13 (CF_UNICODETEXT).

INSTALLATION on a UNIX-ALIKE:

• The PDF manuals (if built) can be compacted by the new target
  make compact-pdf (at the top level or in directory doc/manual).

• There is now configure support for LLVM clang 15 on Linux, which
  defaults to position-independent (PIE) executables whereas
  gfortran does not.

• Many small changes to ease compilation (and suppress warnings)
  with LLVM clang 15.

BUG FIXES:

• Rscript -e would fail if stdin were closed (Reported by Henrik
  Bengtsson.)

• qt(*, log.p=TRUE) in outer tails no longer produces NaN in its
  final steps, thus fixing PR#18360.

• tools::Rd2latex() now escapes hashes and ampersands when writing
  URLs, fixing LaTeX errors with such URLs in \tabular.

• When isGeneric(f, fdef=*) is used with mismatching names, the
  warning is better understandable; reported (with fix) in PR#18370
  by Gabe Becker.

• poly(x, n) now works again (and is now documented) when x is a
  "Date" or "POSIXct" object, or of another class while fulfilling
  mode(x) == "numeric". This also enables poly(x, *, raw=TRUE) for
  such variables. Reported by Michael Chirico to R-devel.

• write.table(), write.csv() and write.csv2() restore their
  numerical precision (internal equivalent of digits = 15) after an
  interrupt (PR#18384).

• One can now read also byte FF from a clipboard connection
  (PR#18385).

• source("") and source(character()) now give more helpful error
  messages.

• R CMD check --as-cran set _R_CHECK_TIMINGS_ too late to have the
  intended effect.

• as.POSIXlt(x) now also works with very large dates x, fixing
  PR#18401 reported by Hannes Mühleisen.

• Files can now be extracted even from very large zip archives
  (PR#18390, thanks to Martin Jakt).

• Non-finite objects of class "POSIXlt" are now correctly coerced
  to classes "Date" and "POSIXct"; following up on the extension to
  format() them correctly.

• Added methods for is.finite(), is.infinite() and is.nan() for
  "POSIXlt" date-time objects.

BUG FIXES on Windows:

• Non-ASCII characters are now properly displayed on Windows in
  windows created using GraphApp via e.g. winDialogString thanks to
  a workaround for an at least surprising Windows behavior with
  UTF-8 as the system encoding (PR#18382).

• Find and replace operations work again in the script editor in
  Rgui on Windows.

• Computation of window size based on requested client size in
  GraphApp when running in a multi-byte locale on Windows has been
  fixed (regression in R 4.2.0 for users of systems where R 4.1
  used a single-byte locale). Rgui again respects the number of
  console rows and columns given in Rconsole file.

• Rterm support for Alt+xxx sequences has been fixed to produce the
  corresponding character (only) once. This fixes pasting text with
  tilde on Italian keyboard (PR#18391).