Convert to composite action over stack-action

This is an minor improvement over archiving as-is with documentation
pushing users to `stack-action`. As a `composite`, this action should
require little-to-no maintenance; only if/when `stack-action` has a
major version bump.

The known downsides to this approach are:

1. We lost the `cache-hit` output
2. Building with `--dry-run` does do some more work than before
3. The `setup` step installs GHC if necessary

Of these, only (3) is a minor concern since it does add a bit of time.

However:

* It only happens on un-cached runs, and
* If we assume users of this action will in fact build something
  somewhere, we are not _adding_ this time, only moving it

Therefore, we consider this acceptable.

Author: pbrisbin

.github/workflows/ci.yml

@@ -20,7 +20,6 @@ jobs:
           working-directory: example
       - name: Build
         run: |
-          echo "cache-hit: ${{steps.stack-cache.outputs.cache-hit}}"
           find .
           mkdir -p ~/.stack ./.stack-work ./package/.stack-work
           echo "An artifact" > ~/.stack/artifact

.github/workflows/example.yml

@@ -2,14 +2,28 @@
 
 Cache step for Stack-based Haskell projects on GitHub Actions.
 
-**NOTE**: if you are using `freckle/stack-action@v4` or newer, you do not
-need this action as its own step. That version of that action handles all
-caching internally, and better.
+> [!NOTE]
+>
+> As of `@v3`, this action is a `composite` pass-through to `stack-action`:
+>
+> ```yaml
+> - uses: freckle/stack-action@v6
+>   env:
+>     STACK_YAML: ${{ inputs.stack-yaml }}
+>   with:
+>     working-directory: ${{ inputs.working-directory }}
+>     cache-prefix: ${{ inputs.prefix }}
+>     stack-build-arguments: --dry-run
+>     install-stack: false
+>     upgrade-stack: false
+> ```
+>
+> You could consider replacing use of this action with that directly.
 
 ## Usage
 
 ```yml
-uses: freckle/stack-cache-action@v2
+uses: freckle/stack-cache-action@v3
 ```
 
 ## Behavior
@@ -29,10 +43,6 @@ uses: freckle/stack-cache-action@v2
 - `working-directory`: Useful in monorepositories
 - `prefix`: A prefix to include on keys; useful for cache busting or versioning
 
-## Outputs
-
-- `cache-hit`: indicates a full cache hit on the primary key
-
 ## Further Reading
 
 See https://tech.freckle.com/2021/05/18/haskell-on-actions/ for a short tutorial.

.gitignore

@@ -1,10 +1,6 @@
 name: "Stack cache"
 author: "freckle"
 description: "Caching Action for Stack-based Haskell projects"
-runs:
-  using: "node16"
-  main: "dist/restore/index.js"
-  post: "dist/save/index.js"
 inputs:
   stack-yaml:
     description: "Path to stack.yaml"
@@ -18,6 +14,17 @@ inputs:
     description: "A prefix to include on keys; useful for cache busting or versioning"
     required: false
     default: ""
-outputs:
-  cache-hit:
-    description: "A boolean value to indicate an exact match was found for the primary key"
+runs:
+  using: "composite"
+  steps:
+    - uses: freckle/stack-action@v5
+      env:
+        STACK_YAML: ${{ inputs.stack-yaml }}
+      with:
+        working-directory: ${{ inputs.working-directory }}
+        cache-prefix: ${{ inputs.cache-prefix }}
+
+        # Avoid other stack-action behavior, as much as we can
+        stack-build-arguments: --dry-run
+        install-stack: false
+        upgrade-stack: false