Give the action some outputs

Give the action some outputs, so the scallywag build action doesn't have
to guess/hardcode those internal values.

(Note that locating output values relies on the id assigned to a step, a
point which the official documentation could stand to be clearer on)

Author: jon-turney

.github/workflows/test.yml

@@ -301,3 +301,43 @@ jobs:
 
     - name: Run test shell script
       run: C:\cygwin\bin\bash.exe /cygwin-install-action-test.sh
+
+  outputs-test:
+    runs-on: windows-latest
+
+    name: 'Test outputs'
+
+    steps:
+    - run: git config --global core.autocrlf input
+
+    - uses: actions/checkout@v4
+
+    - name: Install Cygwin
+      id: cygwin-install
+      uses: ./
+
+    - name: Verify Outputs
+      run: |
+        echo "setup executable is at: ${SETUP}"
+        echo "cygwin install root directory is: ${ROOT}"
+        echo "cygwin package cache directory is: ${CACHE}"
+
+        if [[ "${SETUP}" != "D:\setup.exe" ]]; then
+          echo "unexpected value for 'setup' output"
+          exit 1
+        fi
+
+        if [[ "${ROOT}" != "D:\cygwin" ]]; then
+          echo "unexpected value for 'root' output"
+          exit 1
+        fi
+
+        if [[ "${CACHE}" != "D:\cygwin-packages" ]]; then
+          echo "unexpected value for 'package-cache' output"
+          exit 1
+        fi
+      shell: bash -o igncr '{0}'
+      env:
+        SETUP: ${{ steps.cygwin-install.outputs.setup }}
+        ROOT: ${{ steps.cygwin-install.outputs.root }}
+        CACHE: ${{ steps.cygwin-install.outputs.package-cache }}

README.md

@@ -108,6 +108,18 @@ These options are very unlikely to be useful except in some very isolated
 circumstances, such as using the [Cygwin Time
 Machine](http://www.crouchingtigerhiddenfruitbat.org/Cygwin/timemachine.html).
 
+Outputs
+-------
+
+| Output        | Description
+| ------------- | -----------------------------------------
+| package-cache | Package cache directory
+| root          | Root directory of the Cygwin installation (equal to the install-dir input)
+| setup         | Cygwin setup executable pathname
+
+Footnotes
+---------
+
 [1] The
 [Workflow documentation](https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#exit-codes-and-error-action-preference)
 suggests you should also use bash options `-eo pipefail`, omitted here for clarity

action.yml

@@ -46,10 +46,22 @@ inputs:
     required: false
     default: ''
 
+outputs:
+  setup:
+    description: Pathname of the Cygwin setup executable
+    value: ${{ steps.cygwin-install-action.outputs.setup }}
+  root:
+    description: Root directory of Cygwin installation (equal to install-dir input)
+    value: ${{ steps.cygwin-install-action.outputs.root }}
+  package-cache:
+    description: Package cache directory
+    value: ${{ steps.cygwin-install-action.outputs.package-cache }}
+
 runs:
   using: "composite"
   steps:
-    - run: |
+    - id: cygwin-install-action
+      run: |
         $ErrorActionPreference = 'Stop'
         $platform = '${{ inputs.platform }}'
         $platform = $platform -replace '^(x64|amd64)$', 'x86_64'
@@ -143,14 +155,16 @@ runs:
           $installDir = '${{ inputs.install-dir }}'
         }
 
+        $packageDir = "$vol\cygwin-packages"
+
         $packages = '${{ inputs.packages }}'
         $pkg_list = $packages.Split('', [System.StringSplitOptions]::RemoveEmptyEntries)
         $pkg_list = $pkg_list | % { $_.Trim() }
         $pkg_list = $pkg_list | % { $_.Trim(',') }
 
         $args = @(
          '-qnO',
-         '-l', "$vol\cygwin-packages",
+         '-l', "$packageDir",
          '-R', "$installDir"
         )
 
@@ -212,6 +226,12 @@ runs:
 
         # run login shell to copy skeleton profile files
         & "$installDir\bin\bash.exe" --login
+
+        # set outputs
+        echo "setup=$setupExe" >> $env:GITHUB_OUTPUT
+        echo "root=$installDir" >> $env:GITHUB_OUTPUT
+        echo "package-cache=$packageDir" >> $env:GITHUB_OUTPUT
+
       shell: powershell
 
 branding: