Synchronizing Subtrees: Pushing and Pulling Changes

The [josh] tool is an alternative to git subtrees, which manages git history in a different way and scales better to larger repositories. Specific tooling is required to work with josh, you can check out the `miri` or `rust-analyzer` scripts linked above for inspiration. If you want to migrate a repository dependency from `git subtree` or `git submodule` to josh, you can check out [this guide](https://hackmd.io/7pOuxnkdQDaL1Y1FQr65xg). Below you can find a guide on how to perform push and pull synchronization with the main rustc repo using `git subtree`, although these instructions might differ repo from repo. ### Synchronizing a subtree Periodically the changes made to subtree based dependencies need to be synchronized between this repository and the upstream tool repositories. Subtree synchronizations are typically handled by the respective tool maintainers. Other users are welcome to submit synchronization PRs, however, in order to do so you will need to modify your local git installation and follow a very precise set of instructions. These instructions are documented, along with several useful tips and tricks, in the [syncing subtree changes][clippy-sync-docs] section in Clippy's Contributing guide. The instructions are applicable for use with any subtree based tool, just be sure to use the correct corresponding subtree directory and remote repository. The synchronization process goes in two directions: `subtree push` and `subtree pull`. A `subtree push` takes all the changes that happened to the copy in this repo and creates commits on the remote repo that match the local changes. Every local commit that touched the subtree causes a commit on the remote repo, but is modified to move the files from the specified directory to the tool repo root. A `subtree pull` takes all changes since the last `subtree pull` from the tool repo and adds these commits to the rustc repo along with a merge commit that moves the tool changes into the specified directory in the Rust repository. It is recommended that you always do a push first and get that merged to the tool master branch. Then, when you do a pull, the merge works without conflicts. While it's definitely possible to resolve conflicts during a pull, you may have to redo the conflict resolution if your PR doesn't get merged fast enough and there are new conflicts. Do not try to

The `josh` tool offers an alternative to git subtrees for managing repository dependencies, particularly for large repositories. Synchronizing subtrees involves pushing changes from the main rustc repository to the tool's upstream repository and pulling changes from the tool's repository into the rustc repository. The recommended approach is to always push changes first and merge them to the tool's master branch to avoid conflicts during the pull. The process involves modifying the local git installation and following precise instructions, which are detailed in Clippy's Contributing guide and are applicable to any subtree-based tool.