Reuse build cache for the whole branch

.gitlab-ci.yml

@@ -7,7 +7,7 @@ stages:
 
 .rust_template: &rust_template
   cache:
-    key: "$CI_JOB_NAME-$CI_COMMIT_REF_NAME"
+    key: "$CI_COMMIT_REF_SLUG"
     paths:
       - cargo/
       - target/