cache prepopulation (#386)

* test (ci): cache prepopulation with debug info

* test (ci): remove CARGO_HOME caching

* test (ci): fix x mode for the script

* change (ci): undebug

.gitlab-ci.yml

@@ -14,7 +14,6 @@ stages:
 variables:
   GIT_STRATEGY:                    fetch
   GIT_DEPTH:                       100
-  CARGO_HOME:                      "/ci-cache/${CI_PROJECT_NAME}/cargo/${CI_JOB_NAME}"
   CARGO_TARGET_DIR:                "/ci-cache/${CI_PROJECT_NAME}/targets/${CI_COMMIT_REF_NAME}/${CI_JOB_NAME}"
   CI_SERVER_NAME:                  "GitLab CI"
   REGISTRY:                        registry.parity.io/parity/infrastructure/scripts
@@ -35,15 +34,7 @@ variables:
     - rustc -vV
     - rustup show
     - bash --version
-    # if there is no directory for this $CI_COMMIT_REF_NAME/$CI_JOB_NAME
-    # create such directory and
-    # create hardlinks recursively of all the files from the master/$CI_JOB_NAME if it exists
-    - if [[ ! -d $CARGO_TARGET_DIR ]]; then
-        mkdir -p /ci-cache/${CI_PROJECT_NAME}/targets/${CI_COMMIT_REF_NAME};
-        cp -al /ci-cache/${CI_PROJECT_NAME}/targets/${CI_DEFAULT_BRANCH}/${CI_JOB_NAME}
-          /ci-cache/${CI_PROJECT_NAME}/targets/${CI_COMMIT_REF_NAME} ||
-          echo "_____No such target dir, proceeding from scratch_____";
-      fi
+    - ./scripts/pre_cache.sh
     - sccache -s
   only:
     - master

scripts/pre_cache.sh

+#!/bin/bash
+
+set -u
+
+# if there is no directory for this $CI_COMMIT_REF_NAME/$CI_JOB_NAME
+# create such directory and
+# copy recursively all the files from the newest dir which has $CI_JOB_NAME, if it exists
+if [[ ! -d $CARGO_TARGET_DIR ]]; then
+  mkdir -p "/ci-cache/$CI_PROJECT_NAME/targets/$CI_COMMIT_REF_NAME";
+  FRESH_CACHE=$(find "/ci-cache/$CI_PROJECT_NAME/targets" -mindepth 2 -maxdepth 2 \
+    -type d -name "$CI_JOB_NAME"  -exec stat --printf="%Y\t%n\n" {} \; |sort -n -r |head -1 |cut -f2);
+  if [[ -d $FRESH_CACHE ]]; then
+    echo "____Using" "$FRESH_CACHE" "to prepopulate the cache____";
+    time cp -r "$FRESH_CACHE" "$CARGO_TARGET_DIR";
+  else
+    echo "_____No such targets dir, proceeding from scratch_____";
+  fi
+else
+  echo "____No need to prepopulate CARGO_TARGET_DIR cache____";
+fi