Create DXC Updagrade Readme.md

Author: devshgraphicsprogramming

3rdparty/dxc/Readme.md

@@ -0,0 +1,89 @@
+# How to update the DXC module
+
+## FIRST TIME SETUP: Make sure you have the correct remotes!
+
+The following submodules as initialized on your system should have `origin` pointing at the `[email protected]:Devsh-Graphics-Programming` fork.
+
+Then a remote `Khronos` for the SPIR-V submodules, and `Microsoft` for the DXC.
+
+If they don't then you can correct that with `git remote add [RemoteName] [email protected]:[Organisation]/[Repo-Name].git` and `git remote remove [RemoteName]`
+
+## IF YOU GET `There is no tracking information for the current branch`
+
+just make the branch track the origin
+```
+git branch --set-upstream-to=origin/[BranchName] [BranchName]
+```
+
+## Its Basically an Depth First Search with a Prologue and Epilogue
+
+```
+checkout correct branch HEAD
+[optional] Merge latest stuff from original project
+recurse()
+commit
+push
+```
+
+### First make sure you're on some Nabla branch Head
+
+Just `git pull` and make sure you're tracking a branch.
+
+### Make sure DXC is tracked and pointing at HEAD
+
+```
+cd ./3rdparty/dxc/dxc
+git fetch
+git checkout devshFixes
+git pull
+```
+
+### SPIR-V Headers: track & get latest head, merge latest upstream, commit and push
+
+```
+cd ./external/SPIRV-Headers
+git fetch
+git checkout header_4_hlsl
+git pull
+git pull Khronos main
+git commit -m "latest Khronos `main` merge"
+git push
+```
+
+### SPIR-V Tools: track & get latest head, merge latest upstream, commit and push
+
+```
+cd ../SPIRV-Tools
+git fetch
+git checkout main
+git pull
+git pull Khronos main
+git commit -m "latest Khronos `main` merge"
+git push
+```
+
+### Back to DXC and commit the submodule pointer changes
+
+```
+cd ..
+git add .
+git commit -m "Update SPIR-V Headers and Tools"
+cd ..
+[optional] git pull Microsoft main
+[optional] git commit -m "merge upstream from Microsoft"
+git push
+```
+
+The reason the upstream from Microsoft is optional is because it might break our Clang hacks like:
+- abuse of `__decltype`
+- `inout` working like a reference, but only sometimes
+- abuse of reference type
+
+### Finally commit the change of DXC commit pointer to Nabla
+
+```
+cd ..
+git add dxc
+git commit -m "Updated DXC"
+git push
+```