Add gulrak filesystem, a c++17 compliant std::filesystem polyfill.

[akrieger]

Summary

None

Purpose of change

Add ghc filesystem, a c++17 compliant std::filesystem polyfill, and convert handwritten filesystem helpers to use it. This helps with writing more portable code and adds a functional path class too.

Testing

Create a new game, load a game, save and reload the game.

Additional context

Prerequisite for #50143.

[akrieger]

I'm not sure the best way to exclude these sources from clang-tidy. Maybe appropriate to create a third_party directory to shove files like these and others which should be excluded from tidy and astyle?

[kevingranade]

This comment outlines how to set header-only libraries as system headers in cmake https://stackoverflow.com/a/64748887/280690
IIRC a separate directory won't work since it's going to trace the header inclusions anyway.

[akrieger]

I would never have figured out that's how clang-tidy picks those up. Thanks!

[akrieger]

Turns out I had to add extra arguments to clang-tidy-wrapper.sh because build.sh was just passing each file in isolation to clang-tidy without any extra arguments. At first it was complaining it couldn't find <ghc/fs_std.hpp>, adding -Isrc/third-party to the wrapper made it find the header but complained, changing it to -isystem src/third-party silenced the warnings.

[akrieger]

+ ./build-scripts/files_changed
+ set +x
Analyzing changed files
No files to analyze

Hm. That seems wrong. But my changes to files_changed should've only been fixes or new behavior. HEAD^2 syntax didn't seem to work in my vm, changing it to ~2 did.

[akrieger]

Reverted changes to build-scripts/files_changed, fixed tests Makefile compilation.

[akrieger]

+ ./build-scripts/files_changed
LICENSE.txt
Makefile
build-scripts/clang-tidy-wrapper.sh
src/CMakeLists.txt
src/filesystem.cpp
src/filesystem.h
+ set +x
src/third-party/CMakeLists.txt
src/third-party/ghc/LICENSE
src/third-party/ghc/filesystem.hpp
src/third-party/ghc/fs_fwd.hpp
src/third-party/ghc/fs_impl.hpp
src/third-party/ghc/fs_std.hpp
src/third-party/ghc/fs_std_fwd.hpp
src/third-party/ghc/fs_std_impl.hpp
tests/Makefile
Analyzing changed files
3489 warnings generated.
Analyzing remaining files because build-scripts/clang-tidy-wrapper.sh was changed

Better, but now the whole codebase is going to barf.

[akrieger]

clang-tidy build is passing on the new code, it's just failing on the rest of the repo because I actually touched the clang-tidy script so it's rerunning the checks. I've fixed every build failure I've found so far, I just haven't managed to get all the builds to run without timing out eventually.

[akrieger]

Reverted the change to the clang-tidy wrapper since it's not needed after fixing the cmake build finally.

[akrieger]

This is finally ready and passing CI. The only thing I'm not sure about is the exact place in the Makefile that is best to add the include path.

[akrieger]

Rebased, moved include directory flags to CPPFLAGS.

[ZhilkinSerg]

Android build is broken - https://github.com/CleverRaven/Cataclysm-DDA/runs/3449081942

 /home/runner/work/Cataclysm-DDA/Cataclysm-DDA/android/app/jni/src/../../../../src/filesystem.cpp:16:10: fatal error: 'ghc/fs_std_fwd.hpp' file not found
  #include <ghc/fs_std_fwd.hpp>

Probably src/third-party should be mentioned in Android Makefile.

[kevingranade]

This pull request has been mentioned on Cataclysm: Dark Days Ahead. There might be relevant details there:

https://discourse.cataclysmdda.org/t/window-version-dosent-support-creating-world-use-chinese-characators/26929/2