Determine default cache map from Dockerfile

README.md

@@ -133,6 +133,7 @@ Save 'RUN --mount=type=cache' caches on GitHub Actions or other CI platforms
 Options:
   --extract      Extract the cache from the docker container (extract step). Otherwise, inject the cache (main step)
   --cache-map    The map of actions source to container destination paths for the cache paths
+  --dockerfile   The Dockerfile to use for the auto-discovery of cache-map. Default: 'Dockerfile'
   --scratch-dir  Where the action is stores some temporary files for its processing. Default: 'scratch'
   --skip-extraction  Skip the extraction of the cache from the docker container
   --builder     The name of the buildx builder. Default: 'default'

action.yml

@@ -2,8 +2,10 @@ name: Inject/Extract Cache
 description: "Injects the cached data into the docker build(x|kit) process"
 inputs:
   cache-map:
-    required: true
-    description: "The map of actions source paths to container destination paths or mount arguments"
+    description: "The map of actions source paths to container destination paths or mount arguments. If not provided, the Dockerfile will be used to determine the cache paths."
+  dockerfile:
+    description: "The Dockerfile to use for the auto-discovery of cache-map. Default: `Dockerfile`"
+    default: "Dockerfile"
   cache-source:
     deprecationMessage: "Use `cache-map` instead"
     description: "Where the cache is stored in the calling workspace. Default: `cache`"

package.json

@@ -31,6 +31,8 @@
   },
   "dependencies": {
     "@actions/core": "~1.5.0",
+    "dockerfile-ast": "^0.7.0",
+    "fs": "0.0.1-security",
     "mri": "^1.2.0",
     "spawn-please": "^3.0.0"
   },