@@ -11,3 +11,32 @@ The procedure for performing subtree synchronizations is documented [here][rdg-j
 ## Pushing changes to `rust-lang/rust`
 
 If the used GCC commit (recorded in `libgccjit.version`) changed in `rustc_codegen_gcc`, then you will have to update the `gcc` submodule in the `rust-lang/rust` repository in the push sync PR. The CI in `rust-lang/rust` should ensure that these two commit references match. You can simply update the `gcc` submodule commit and push it to your push sync PR once it has been created.
+
+## Environment variables to make things easier
+
+To avoid passing through github `https` interface, create a file named `josh.gitconfig` (for example at `$HOME/.config/git/josh.gitconfig`) which contains:
+
+```gitconfig
+[url "git@github.com:"]
+insteadOf = "https://github.com/"
+
+[include]
+path = ~/.gitconfig
+path = ~/.config/git/config
+```
+
+Then refer to it using the `GIT_CONFIG_GLOBAL` environment variable.
+
+And to prevent cloning the rust repository every time, set the `RUSTC_GIT` environment variable to point to your local copy of the `rust` repository. The path needs to be absolute!
+
+Then running the command looks like:
+
+```bash
+GIT_CONFIG_GLOBAL=$HOME/.config/git/josh.gitconfig RUSTC_GIT=/my/local/rust-fork rustc-josh-sync push <branch name> <rust fork owner>
+```
+
+So if your github account name is "tadam" and you want to push to a branch named "cg_gcc-subtree-sync", the command will be:
+
+```bash
+GIT_CONFIG_GLOBAL=$HOME/.config/git/josh.gitconfig RUSTC_GIT=/my/local/rust-fork rustc-josh-sync push cg_gcc-subtree-sync tadam
+```