dev

TODO:

```
/__w/install-action/install-action/.//main.sh: line 81: syntax error: unexpected "(" (expecting "}")
```

action.yml

@@ -21,32 +21,32 @@ inputs:
 runs:
   using: composite
   steps:
-    - run: |
+    - name: Prepare
+      id: prepare
+      run: |
         set -eu
         if ! command -v bash >/dev/null; then
-          if grep -Eq '^ID=alpine' /etc/os-release; then
-            printf '::group::Install packages required for install-action (bash)\n'
-            # NB: sync with apk_install in main.sh
-            if command -v sudo >/dev/null; then
-              sudo apk --no-cache add bash
-            elif command -v doas >/dev/null; then
-              doas apk --no-cache add bash
-            else
-              apk --no-cache add bash
+          if command -v busybox >/dev/null; then
+            if test -n "${GITHUB_OUTPUT:-}"; then
+              printf 'shell=busybox sh -e {0}\n' >>"${GITHUB_OUTPUT}"
+              exit
             fi
-            printf '::endgroup::\n'
-          else
-            printf '::error::install-action requires bash\n'
-            exit 1
           fi
+          printf '::error::install-action requires bash or busybox\n'
+          exit 1
         fi
       shell: sh
       if: runner.os == 'Linux'
-    - run: bash --noprofile --norc "${GITHUB_ACTION_PATH:?}/main.sh"
-      shell: bash
+    - run: |
+        case "${CURRENT_SHELL}" in
+          busybox*) busybox sh "${GITHUB_ACTION_PATH:?}/main.sh" ;;
+          *) bash --noprofile --norc "${GITHUB_ACTION_PATH:?}/main.sh" ;;
+        esac
+      shell: ${{ steps.prepare.outputs.shell || 'bash' }}
       env:
         INPUT_TOOL: ${{ inputs.tool }}
         INPUT_CHECKSUM: ${{ inputs.checksum }}
         INPUT_FALLBACK: ${{ inputs.fallback }}
         DEFAULT_GITHUB_TOKEN: ${{ github.token }}
         ACTION_USER_AGENT: ${{ github.action_repository }} (${{ github.action_ref }})
+        CURRENT_SHELL: ${{ steps.prepare.outputs.shell }}