2.53.0

2.53.0 is a significant release with new features (xattr, ACLs), a change to GTK3, and many bugfixes. All users are urged to upgrade.

• OCaml >= 4.08 is required to build unison.
• unison can be built with (unreleased) OCaml 5.
• Change GUI to use GTK3 (via lablgtk3) instead of GTK2 (via lablgtk2)
• Add support for syncing extended attributes.
• Add support for syncing ACLs.
• On Windows, add the ability to build unison as a hybrid
  application (GUI application attached to a text console) by
  defining UI_WINOS=hybrid (see src/Makefile). Add this to CI.
  (Doing this for non-Windows is unnecessary as all applications,
  both GUI and non-GUI, are always executed with a connection to
  stdout/stderr. GUI-only applications (ie, no stdout/stderr) is a
  Windows-only concept.)
• Notable bugfixes
  • Merge results are stored in archive more accurately.
  • Windows \\?\ paths now work correctly (including \\?\Volume{GUID}\ paths).
• CI changes
  • The macOS binaries are properly signed.
  • Add workaround for bugs in the github CI Windows builds, one of
    which resulted in the 2.52.1 GUI version failing, in the Windows
    CI build artifacts. (This does not affect platforms other than
    Windows, and may not affect other Windows builds.)
• Changes that should not affect behavior
  • Clean up a variety of unmaintained and unused bits, mainly
    build-related.
  • OCaml's Unix library is now extensively used also on
    Windows. This allowed removal of large amount of
    Windows-specific OCaml and mainly C code.