Update circle.yml

Author: sfackler

circle.yml

@@ -1,26 +1,40 @@
+restore_registry: &RESTORE_REGISTRY
+  restore_cache:
+    key: registry
+save_registry: &SAVE_REGISTRY
+  save_cache:
+    key: registry-{{ .BuildNum }}
+    paths:
+    - /usr/local/cargo/registry/index
+deps_key: &DEPS_KEY
+  key: deps-{{ checksum "~/rust-version" }}-{{ checksum "Cargo.lock" }}
+restore_deps: &RESTORE_DEPS
+  restore_cache:
+    <<: *DEPS_KEY
+save_deps: &SAVE_DEPS
+  save_cache:
+    <<: *DEPS_KEY
+    paths:
+    - target
+    - /usr/local/cargo/registry/cache
+
 version: 2
 jobs:
   build:
     working_directory: ~/build
     docker:
-      - image: jimmycuadra/rust:1.19.0
+      - image: rust:1.20.0
+        environment:
+          RUSTFLAGS: -D warnings
       - image: postgres:9.6
         environment:
           POSTGRES_PASSWORD: password
     steps:
       - checkout
-      - restore_cache:
-          key: registry
+      - *RESTORE_REGISTRY
       - run: cargo generate-lockfile
-      - save_cache:
-          key: registry-{{ epoch }}
-          paths:
-            - ~/.cargo/registry/index
-      - restore_cache:
-          key: dependencies-1.19-{{ checksum "Cargo.lock" }}
+      - *SAVE_REGISTRY
+      - run: rustc --version > ~/rust-version
+      - *RESTORE_DEPS
       - run: cargo test
-      - save_cache:
-          key: dependencies-1.19-{{ checksum "Cargo.lock" }}
-          paths:
-            - target
-            - ~/.cargo/registry/cache
+      - *SAVE_DEPS