From 76bc70e50bf0c7b024a3039df6fa722973b7217f Mon Sep 17 00:00:00 2001
From: Bradley Lowekamp <blowekamp@mail.nih.gov>
Date: Thu, 22 Mar 2018 14:27:01 -0400
Subject: [PATCH] ENH: Update CircleCI external data cache

Introduce Yaml anchors to enable reuse of common steps.

The previous external data circleci cache was never being updated.

Obtain the most recent commit to modify a md5 or sha512 file. The hash
of this commit message is used for the hash key of the external data
CircleCI cache.

Change-Id: I29e35b15bfd3c3d2799ce835bd4a8dedd371f49a
---
 .circleci/config.yml | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 157442ca824..a6abacdf32a 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,3 +1,16 @@
+referenced:
+  generate-hash-step: &generate-hash-step
+    run:
+      name: Generate external data hash
+      command: |
+        cd ITK
+        find . -name \*.md5 -o -name \*.sha512 -print0 | xargs -d "\n" git log -n 1 | tee /home/circleci/external-data.hashable
+  restore-data-step: &restore-data-step
+     restore_cache:
+       keys:
+         - 'v1-external-data-{{ checksum "/home/circleci/external-data.hashable" }}'
+         - 'v1-external-data'
+
 version: 2
 jobs:
   build:
@@ -19,9 +32,8 @@ jobs:
     steps:
       - checkout:
           path : ~/ITK
-      - restore_cache:
-          keys:
-            - external-data
+      - *generate-hash-step
+      - *restore-data-step
       - restore_cache:
           keys:
             - ccache-{{ arch }}-{{ .Branch }}
@@ -78,5 +90,5 @@ jobs:
           key: 'ccache-{{ arch }}-{{ .Branch }}-{{ epoch }}'
           paths: [ "/home/circleci/.ccache" ]
       - save_cache:
-          key: 'external-data'
+          key: 'v1-external-data-{{ checksum "/home/circleci/external-data.hashable" }}'
           paths: [ "/home/circleci/.ExternalData" ]