Version 0.3.0

  * Support for High Fidelity Builds (HFB).

    The C++ compiler and link rules now detect when the compiler, options, or
    input file set have changed and trigger the update of the target. Some
    examples of the events that would now trigger an automatic update:

    * Compiler change (e.g., g++ to clang++), upgrade, or reconfiguration.
    * Change of compile/link options (e.g., -O2 to -O3).
    * Rename of a source file name (e.g., foo.cpp to foo.cxx).
    * Removal of a file from a library/executable.

  * Support for the Intel C++ compiler on Linux.

  * Command line options, variables, and buildspec can now be specified in any
    order. This is especially useful if you want to re-run the previous
    command with -v or add a forgotten config variable:

    b test -v
    b configure config.cxx=clang++

  * Implement C++ compiler detection. Currently recognized compilers and their
    ids (in the <type>[-<variant>] form):

      gcc            GCC
      clang          Vanilla Clang
      clang-apple    Apple Clang (and the g++ "alias")
      icc            Intel icpc
      msvc           Microsoft cl.exe

    The compiler id, version, and other information is available via the
    following build system variables:

    cxx.id
    cxx.id.{type,variant}
    cxx.version
    cxx.version.{major,minor,patch,build}
    cxx.signature
    cxx.checksum
    cxx.target
    cxx.target.{cpu,vendor,system,version,class}

  * Implement ar/ranlib detection. The following information is available
    via the build system variables:

    bin.ar.signature
    bin.ar.checksum
    bin.ranlib.signature
    bin.ranlib.checksum

  * On update for install the C++ link rule no longer uses the -rpath
    mechanism for finding prerequisite libraries.

  * Set build.host, build.host.{cpu,vendor,system,version,class} build system
    variables to the host triplet. By default it is set to the compiler target
    build2 was built with but a more precise value can be obtained with the
    --config-guess option.

  * Set build.version, build.version.{major,minor,patch,release,string} build
    system variables to the build2 version.

  * Extracted header dependencies (-M*) are now cached in the auxiliary
    dependency (.d) files rather than being re-extracted on every run. This
    speeds up the up-to-date check significantly.

  * Revert back to only cleaning targets in subdirectories.

    Cleaning everything as long as it is in the same strong amalgamation had
    some undesirable side effects. For example, in bpkg, upgrading a package
    (which requires clean/reconfigure) led to all its prerequisite being
    cleaned as well and then rebuilt. That was very surprising, to say the
    least.

  * Allow escaping in double-quoted strings.

Version 0.2.0

  * First public release.