build(ci): preserve rust version when merging (#612)

.github/actions/install_rust/action.yml

@@ -1,4 +1,4 @@
-# Installs rust toolchain. In order to set/fix the version, edit DEFAULT_TOOLCHAIN env variable.
+# Installs rust toolchain with the version defined in .github/actions/install_rust/rust_version.txt.
 inputs:
   components:
     description: "An optional parameter that will be sent to dtolnay/rust-toolchain."
@@ -9,7 +9,7 @@ runs:
   using: "composite"
   steps:
     - name: Define toolchain
-      run: echo "DEFAULT_TOOLCHAIN=stable"  >> $GITHUB_ENV
+      run: echo "DEFAULT_TOOLCHAIN=$(cat .github/actions/install_rust/rust_version.txt)" >> $GITHUB_ENV
       shell: bash
     - name: install rust toolchain with given components
       if: "${{ inputs.components != '' }}"

.github/actions/install_rust/rust_version.txt

@@ -0,0 +1 @@
+stable

scripts/merge_branches.py

@@ -16,6 +16,7 @@
 
 FINAL_BRANCH = "main"
 MERGE_PATHS_FILE = "scripts/merge_paths.json"
+FILES_TO_PRESERVE = {".github/actions/install_rust/rust_version.txt"}
 
 
 def load_merge_paths() -> Dict[str, str]:
@@ -114,6 +115,8 @@ def merge_branches(src_branch: str, dst_branch: Optional[str]):
 
     run_command(f"git merge origin/{src_branch}", allow_error=True)
 
+    run_command(f"git checkout origin/{dst_branch} {' '.join(FILES_TO_PRESERVE) }")
+
     run_command("git config --unset merge.conflictstyle")
     run_command("git status -s | grep \"^UU\" | awk '{ print $2 }' | tee /tmp/conflicts")