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+Build Boost
+===========
+
+This GitHub action downloads & builds Boost libraries in your workflow run.
+
+* Downloads a distribution of the specified Boost version and unpacks it.
+* Builds the required libraries using the specified toolset.
+
+Use it in your workflow like this:
+
+    - name: Build Boost
+      uses: egor-tensin/build-boost@v1
+      with:
+        version: 1.71.0
+        libraries: filesystem program_options system
+        platform: x64
+        configuration: Release
+
+* This action uses my other project [cmake-common] to actually download and
+build Boost.
+* GCC is used by default on Linux; on Windows, it's MSVC.
+Specify the `toolset` parameter to use a different toolset.
+* `x64` is the default value for the `platform` parameter and can be omitted.
+Use `x86` if you want to build 32-bit binaries.
+* `Release` is the default value for the `configuration` parameter and can be
+omitted.
+Use `Debug` if you want to build debug binaries.
+* Set `static` to `1` if you want to build static libraries.
+* Set `static-runtime` to `1` if you want to link to the static runtime.
+
+[cmake-common]: https://github.com/egor-tensin/cmake-common
+
+API
+---
+
+| Input          | Value        | Default | Description
+| -------------- | ------------ | ------- | -----------
+| version        | **required** |         | Boost version to build, e.g. `1.71.0`.
+| libraries      | **required** |         | Space-separated list of libraries to build, e.g. `filesystem program_options system`.
+| toolset        | auto         | ✓       | Use GCC on Linux and MSVC on Windows.
+|                | msvc         |         | Use MSVC.
+|                | gcc          |         | Use GCC.
+|                | mingw        |         | Use MinGW-w64.
+|                | clang        |         | Use Clang.
+| platform       | x64          | ✓       | Build 64-bit binaries.
+|                | x86          |         | Build 32-bit binaries.
+| configuration  | Release      | ✓       | Build Release binaries.
+|                | Debug        |         | Build Debug binaries.
+| static         | *other*      | ✓       | Shared libraries.
+|                | 1            |         | Static libraries.
+| static-runtime | *other*      | ✓       | Link to the shared runtime.
+|                | 1            |         | Link to the static runtime.
+| directory      | *empty*      | ✓       | Build in `${{ runner.workspace }}/boost`.
+|                | *other*      |         | Build in a custom directory.
+
+| Output     | Example                                | CMake name       | Description
+| ---------- | -------------------------------------- | ---------------- | -----------
+| root       | D:\a\project\boost                     | BOOST_ROOT       | Root Boost directory.
+| librarydir | D:\a\project\boost\stage\x64\Debug\lib | BOOST_LIBRARYDIR | Directory that contains the built libraries.
+
+Notes
+-----
+
+* [cmake-common] sees *a lot* more testing than this action, while this action
+delegates almost everything to it.
+* You can use my other actions [setup-gcc], [setup-mingw], [setup-clang] to set
+up different toolsets targetting both x86 and x64.
+
+[setup-gcc]: https://github.com/egor-tensin/setup-gcc
+[setup-mingw]: https://github.com/egor-tensin/setup-mingw
+[setup-clang]: https://github.com/egor-tensin/setup-clang
+
+License
+-------
+
+Distributed under the MIT License.
+See [LICENSE.txt] for details.
+
+[LICENSE.txt]: LICENSE.txt