Allow configuring a custom spack repository

Author: viperML

action.yml

@@ -21,13 +21,17 @@ inputs:
     description: "Path to install Spack to"
     required: false
     default: "spack"
+  repository:
+    description: "Repository to use as Spack"
+    required: false
+    default: "spack/spack"
 runs:
   using: "composite"
   steps:
   - name: Checkout Spack
     uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
     with:
-      repository: spack/spack
+      repository: ${{ inputs.repository }}
       path: ${{ inputs.path }}
       ref: ${{ inputs.ref }}