Fix haskell#29: new input cabal-update: false to skip 'cabal update' (

haskell#146)

This commit introduces a new boolean input `cabal-update` that defaults to `true`.  
If set to `false`, the `cabal update` step will be skipped.

The new flag `cabal-update` is proper boolean, it only accepts the YAML 1.2 truth values `true` and `false` (also in captial and uppercase).
This is contrast to other "boolean" flags that are "unset" by default and can be "set" with any non-empty string.

To test that `cabal update` happens, this commit also introduces a new Haskell test project into CI that depends on a common Hackage package (`base-orphans`).

Original commits:
* Fix haskell#29: new input 'cabal-update: false' to turn off 'cabal update'
* Test 'cabal-update: false'
* README: Add 'cabal-update' to table of inputs
* Accept YAML 1.2 booleans as values for 'cabal-update'
* CI: test 'cabal-update: true': project with Hackage dependency
* Default value for 'cabal-update'
* CI: use cabal_update (underscore) in matrix
* Fixup: project with Hackage dependency
* Work around haskell#158
* Extra clarification of boolean vs "boolean" inputs

.github/workflows/workflow.yml

@@ -41,10 +41,13 @@ jobs:
         os: [ubuntu-latest, macOS-latest, windows-latest]
         ghc: ["latest", "8.4.4"]
         cabal: ["latest", "3.2.0.0"]
+        cabal_update: ["false"]
+        # The following tests do not set 'cabal-update', which defaults to 'true' then.
         include:
           - os: ubuntu-latest
             ghc: "8.2.2"
             cabal: "2.4.1.0"
+            cabal_update: "false"
           - os: ubuntu-18.04
             ghc: "7.4.1"
             cabal: "3.4"
@@ -68,24 +71,36 @@ jobs:
             cabal: "3.6"
     steps:
       - uses: actions/checkout@v3
+
       - uses: ./setup
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: ${{ matrix.cabal }}
+          cabal-update: ${{ matrix.cabal_update }}
+
       - name: Test runghc
         run: |
           runghc --version
           runghc __tests__/hello.hs
+
       - name: Build test project
         working-directory: setup/__tests__/project
         run: cabal build
+
       - name: Run test project
         working-directory: setup/__tests__/project
         run: cabal run
+
+      - name: Build and run test with Hackage dependency
+        if:   ${{ matrix.cabal_update != 'false' }}
+        working-directory: setup/__tests__/project-with-hackage-dependency
+        run:  cabal build && cabal run
+
       - name: Show installed versions
         run: |
           cabal --version
           ghc --version
+
       - name: Confirm installed and expected versions match
         shell: bash
         # check that if given in the matrix, the actual version matches: